I have to admit I was not completely pleased with the system that was seen in Mechwarrior 3. That was only a partial mirror to how Battletech worked and ignored the realities (if you'll excuse my use of the word 'real' when referring to imaginary war machines) of actually customizing mechs. Everything was essentially an Omnimech with how that system ran, and you could do even Factory level refits (engine changes) on the field. This is ignoring the fact that the MW3 system was rife with min-maxing. Yes, I find that, to a degree, even Mechwarrior 4 Mercs was a better model (especially after mektek got their hands on it) because it made you think a little more about what machine you wanted to use.
Looking across all the suggestions and discussions about this before, I think one of the best suggestions was to limit customization on various levels by somewhat (not completely) using the refit levels from the board game. Field level refits (class A and B ) would let you, at the very least, switch out weapons so long as the weapons you were switching out took out the same or less space. Maintenance level refits (class C and D) actually let you change electronics packages, engine rating, equipment and weapons (regardless of size), heat sinks, and armor. Factory level refits (Class E and F) were the toughest, but allowed changes to myomer (mech muscle) type, internal structure, case, and even let you change type of engine.
Besides 'time' limitations as the poster before me (Alizabeth Aijou) suggested, something that might help a lot more on top of his time limitation might be a cost factor. It would likely be cheap to switch a PPC for a Large Laser and a Medium Laser (Class A Field Refit). On the flip side, changing out the entire internal structure (skeleton) of a mech (Class F Factory Refit) might quickly be found to be an expensive and time consuming process. With people suggesting Mechs might be lost in battle, this would be a very serious investment, as if you loose your machine, you've lost that much more. On the flip side, someone who did a cheap Class B refit to turn an AC/20 into a pile of lasers would loose much less if their machine were downed in combat.
Edited by Twilight Sparkle, 04 November 2011 - 09:49 AM.