by not allowing LAMs to incorporate most advanced construction materiel is a game mechanic control I do not know how many people were around back then, but I have seen and played with the ORIGINAL LAM rules way back when. Trust me, a Victor LAM was nothing to sneeze at.
by time the MK II LAM construction rules came about that capped LAMs at 55 tons, and it was assumed (but never explicitly stated) that you could use Endo Steel, Ferro Fib, and XL Engines in building your LAMs even with the 55 ton cap, you could create some battlemechs that were wicked little gunships, moving as fast as a Hermes, and packing as much firepower as a crusader.
given no one really gives a damn about balancing BV with pilot skills, and the problem only exacerbated itself as you had unhittable gunships that could hit you every time. when the only way to counter something in a game is to use that same something and hope the dice are on your side, something is inherently wrong with the mechanic.
Now Catalyst compromised in three key areas as far as LAM construction that need to be mentioned.
1st is Double Heat Sinks. without double heat sinks, LAMs are heat pumps that will lose their utility after one air mech super move and three laser strike. at that point you either had to compromise on armor (which the cannon LAMs do) or firepower to keep the machines effective.
2nd is Composite internal structure. facts are facts, this would make any armor breach nearly catastrophic, but you save 5% of the LAMs total weight, at the very least making up for the mass lost to conversion equipment. since LAMs will now and forever be experimental equipment, that is not too far out of the way to go.
3rd is clan technology- the Spectral/Celestial LAMs prove this. Min-Maxers who absolutely need their toys can use clan tech on LAMs, provided they are willing to pay through the nose in BV. you will get that extra edge in range and firepower for less weight, whats not to love?