4 Gauss Rilfes (plus ammo, remember, MWLL gives you a ton for free with each weapon) would equal 52 tons in CBT (1 ton of ammo each). Your standard 10 free heat sinks dissipates this heat no problem.
So, with 52 tons to play with you could get 4 CERPPCs (24 tons), and be left with 28 tons to devote to heat sinks. No mech can mount more than 41 double heat sinks (that is with every possible crit space taken up (except the head) and mounting a 400 rating engine. The mech only needs to dissipate 60 heat, however, so you only need 30 double heat sinks, or 20 tons of extra heat sinks. This leaves you with 8 extra tons to play with. Since heat sinks don't really have critical locations in MWLL, you don't really need to worry about things like endo-steel or ferro-fibrous armor taking up space, nor XL engines for that matter. But, in the spirit of CBT in order for a clan machine to get 52 tons of pod space you are looking at a 100 ton Daishi with 1.5 tons of armor stripped off of it, and it's carrying 5 extra heat sinks already.
Your best bet is to mix Gauss and CERPPCs, 2 of each: 38 tons of weapons and you only need 6 tons of double heat sinks to keep you cool, theoretically. On a Daishi with the 5 default heat sinks already included in that would only cost you 33 tons out of your 50.5 tons of pod space. Plenty of weight to add in the shoulder LRM launcher (4.5 tons w/ammo), and, say, 2 CERMBLs (2 tons). That leaves 11 more tons to slot for ammo, so we'll say it carries 1 extra ton of ammo per weapon, so 8 tons left for extra heat sinks.
End result is:
2 CGauss w/ 2 tons of ammo (3 in MWLL)
2 CERPPC
2 CERMBL
1 CLRM-15 w/ 2 tons of ammo (3 in MWLL)
14 extra Double Heat Sinks (24 total = 48 dissipation)
Builds up 2 heat for gauss, 30 for CERPPC, 5 for LRM-15, and 10 for CERMBL = 47 heat w/ 48 dissipation.
Damage output is ~ 83 damage a turn in CBT (assuming LRM hitting with 9 missiles on average)