Because this is a multiplayer game, IS Mechs need Helm core tech to assist in game balance. Otherwise you would have to balance by number of players, it would have to be 2 IS players for every 1 clan player. And even if MWLL never did IS vs. CLAN asset restrictions, there would be no incentive to us IS mechs.
I would rather not see a "Boating Tax". I'm expecting the game balance gets to the point where you have a natural incentive to break up your loadout. That may require new equipment like Reflective and Reactive Armor "Crap, This guy has reactive armor, and I'm only packing LBX20s!", changes to heat/coolant mechanics "Sure I can fit 4 ERPPCs on here, but I can't even chain fire them without overheating", or default ammo size "Yeah I can fit 4 Gauss rifles, but I only got 8 shots with them".
Back to the Original Topic. I really like how the MWLL Devs have included each Mech's prime variant. Some mechs got upgrades, but those upgrade kept with the spirit of the original design. I think those upgrades are practically required, they are different games with different rules. Even with upgrades I have noticed the prime variants are usually the least popular ones.
Take the Uziel Prime for example. It has a Beagle Active Probe. This piece of tech is worthless in CBT (unless you are playing double blind or other optional rules). Yet its included in MWLL. In MWLL the BAP is actually a useful piece of equipment, but it does not fill the same role as it does in CBT. So It's great the mech appears in MWLL in its canon configuration. Yet I question the reason that piece of equipment is included on a mech who's primary weapons only go out to 700 meters. Should the BAP get swapped with GECM or more tonnage? Maybe. Again, I think its great that MWLL includes canon variants, but I don't think it should be strict adherence. Just keeping with the general spirit of the mech loadout.