I played MW on the SNES and MWII on PC, but when good MW games were coming out I was picking up good LucasArts games, and I wasn't into tabletop when I was a kid. So when I played MWLL, I wasn't drawn in by how accurate to canon it was. The game isn't completely realistic, but it was realistic enough. Trust me, I can relate; it always ticks me off when I see Star Wars games where 3 or so Nebulon-Bs can take on Imperial Star Destroyers.
But I'm gonna spout some heresy and say that I think just looking at the game from the perspective of a Battletech enthusiast will leave you missing a lot of the game's beauty, AND that it is an unrealistic expectation to have. I'll cover the second point first:
Why is canon-accurate BA an unrealistic expectation of MWLL? Anytime you are in a game, press the Tab button. What do you see? You see relatively even teams, with at most 28 players (or more if you want to F the server). HAARP and to a lesser extent Fire Hound's proposal would drastically cut the strength of each Battle Armor, to the point where it is approaching canon-accurate. With only a single anti-mech weapon and 4 missiles, I can tell you that my effectiveness would be cut by at least 80% - that is, I'd be about 1/5 as strong as I was when BA worked properly. While this is also canon-accurate, and you'd expect 3-6 BA to be required to take a mech down, press that Tab button again. Did your team get 5 extra players when you decided to go BA? No, it didn't. It might feel pretty cool to make a BA squad and zoom around the battlefield with your friends, getting the jump on enemies... but the rest of your team will be less-than-happy at effectively being down the equivalent of 2-4 players. Uh oh, a bunch of mechs are incoming to the center base! We need to respond! Wait, no... 5 of our players have an ETA of 4 minutes instead of 30 seconds because they're on foot. And even if they got there, they'd only be the equivalent of one enemy player. And if there is just one enemy player who picks that 6 M.Gun Solitaire, or a Partisan or Huit, or a RIfleman, you and all your friends are going to have a very bad time (especially since you'll give away each other's position and reveal your APC locations extremely quickly).
You might chime in and say that I'd also have a Light M.Gun, so I'd be able to take out other BA. Well as exciting as BA duels can be (when you have a variety of weapons, not when both sides are just shooting each other with BACs), killing BA does almost nothing to help your team win. You might rack up a lot of kills, but at the end of the day, you're dead weight to your team if you concentrate on killing other BA. "But wait, BA are great at disrupting enemy lines and sabotaging slow mechs and vehicles!" Without grenades and with only 1 anti-mech weapon and just 4 missiles, they sure as heck are NOT good at that. Without an mpPPC, you can't catch up to enemies, dodge incoming fire, deal death blows at range, shake enemy cockpits at opportune times, and your DPS is cut by about 1/4. Without infinite SSRMs, your DPS is cut by another 1/4, again you can't shake enemy cockpits at opportune times, and you cannot play mindgames with enemies (target lock warning). Without an mHC, your DPS drops by 1/2. Your proposal basically forces dedicated BA to take a BAC instead of something useful, which is something no good BA player in his right mind would do.
How much of a damage buff do you think you can give BA SSRMs to make up for losing infinite refills? Unless they do Arrow IV damage, it's not enough. BA SSRMs are critical for fighting enemy mechs and enemy BA (especially when every ejected pilot has one of the best anti-BA weapons by default). Just because you might die before firing your fourth SSRM doesn't mean a dedicated BA player does. On each of my lives, I probably connect with between 10 and 60 missiles. Do you really want a single BA SSRM to deal damage equivalent to 15 SSRMs in damage? Frankly, even then it would be a nerf, because I wouldn't have the freedom to use SSRMs for mind games, communication (yes), or BA duels.
Does this really sound fun to you? If you choose an mpPPC, you'll be able to move around the battlefield effectively and dodge enemy fire, but you won't deal enough damage to anything to be worth playing. Or if you choose a mHL, you'll die before you even get into range of an enemy (without mpPPC boosting/dodging) and it'd take you twice as long to walk anywhere. You could choose the AC2, but without an mpPPC you'll never get in range to use it in anything other than single-shot mode. Every other weapon is worthless already. There's no reward to getting close to enemies because you have no grenades. Sure if you get right under their feet you are harder to hit, but you're more likely to get killed by probably-buggy legs. And after running/jetting across the battlefield for 4-8 minutes, you fire your SSRMs 4 times and have to make the trip back. 8-16 minutes of walking to fire four times. Don't say "just ride a light mech into battle!" Try it. Just try it in a real game. It's a fun trick when it doesn't glitch out, and it can be good for returning to base, but unless you want to die the first time your friend is pegged by an enemy, you're better off not doing it. And besides, BA are better off acting stealthy.
So now for the second part; you're missing a part of the game's beauty. Nobody plays every role. I'm not that great in the air and I am garbage with assault mechs. And BA is the most frustrating to get good with, perhaps aside from ASF. So it's no surprise that you haven't really had moments like these:
You're alone in a base being attacked by multiple mechs. Since they can target you through walls, they've had their reticules trained on you the entire time, and they're trying to get a clear shot. If you pop into the air or duck out of cover, you'll be dead before you can pull the trigger (and certainly before you can do much damage). But just running won't work; you have to fight and defeat them somehow. You feather your jump jets to put you just underneath your cover and pull out your mpPPC.
POP! You blast your mpPPC to a far-away wall and hit your JJs a little harder while switching to SSRMs. They'd been itching to pull the trigger, but your sudden acceleration couldn't be accounted for, so their LBX shots graze just past your visor. Just a couple of those pellets would have spelled your end. But your trick was only enough to throw off their first attack, and they quickly swivel to match your speed. One of them gets there first, but you were ready. A single SSRM sizzles out beside your ear and is wire-guided straight into their cockpit. They've shaken a mite, but that's not enough to make him miss so you completely lay off the JJs while you fire another missile to distract him. Four medium lasers sear just over your head. His LBXs will be ready again soon and he is further away from you; if you don't make him your next target, you're as good as dead. You have perhaps 2 seconds to close the distance with him.
But his friend won't make it easy on you. Though slower, his SRMs look pretty scare this close to his feet, now that you are on the ground. He's a little close, but you have no choice; you have to blind him to make your move on your target. So you throw an Inferno Charge at him. It misses but sticks onto an object next to him. The short fuse of the Inferno Charge and its large blast radius make it particularly deadly to... well, yourself, so you reverse jets immediately to hop over his soon-to-be-incoming SRMs with the fuel you had reserved. Explosions below tell you he took his shot, but in just another half-second, he is shaken and shrouded in fire that almost engulfs you as well.
Time's running out on the LBX reload, though, so you pull our your mpPPC and with the last drop of fuel in your jets pop yourself just in front of his feet. He swivels, but at this range you're faster. Backing up a few meters behind him puts you at risk of his blast again, but you have to finish this half of the fight quickly. You carefully hide in his shadow from his friend; just barely eclipsing yourself from fusion-powered retribution. You fling a satchel at his back successfully, but since you've been forced to hold position to hide, your target's torso twist has put his back out of line for your second satchel. Your jump jets have only recovered a little bit of juice. When those C8 charges go off, you'll have put a huge amount of hurt onto your first target. But you're on the clock again. After just a few seconds of safety, you've been tossed back into the fire... the job's not over yet.
That's what it is like to play as a BA in MWLL. It is very often a sublime experience; it's distilled adrenaline laced into a chocolate drumstick. Even the noobiest of noobs can end your life in a single hit, and with only one or two of their weapons. It's a dance of distance and height, gravity and bursts of acceleration. When being stealthy, you have to judge when you might blow your cover by using JJs or mpPPC boosting. Your weapons aren't just sources of damage and they certainly aren't annoyances to manage, they're tools and lifelines! You arc SSRMs over walls in hopes that they will hit. You communicate a known enemy to your team by firing a single missile into the canyon ahead to trigger their AMS. You time your SSRM and mpPPC attacks very carefully to make the screenshake you deal more effective. You laugh maniacally as you casually shut down a mech's night vision on Monument Valley (Night). You laugh maniacally as you're forced to flee from an unexpected group of mechs... but not before giving them the gift of Surprise NARC Beacon. You laugh maniacally when a well-timed mpPPC blast shoves you straight down onto an enemy's torso (not their cockpit because they can magically kill you as long as their cursor is over you), and you start to pull out your mHL (remember kids, attacking someone you've landed on with an mpPPC/SSRMs/grenades/flamers will just kill you). You laugh maniacally as you stand alone in a graveyard of mechs that you just barely survived. And when someone manages to HGauss you in the face when you through you were perfectly safe/mobile, you laugh with them and type "great shot" when you respawn.
So when someone who's been pivotal to the revival of MWLL says "well it's broken because people broke it with successive patches, so instead of fixing it, let's scrap all that and replace it with a simplified, inferior experience," it's a pretty sad day for me.