Well, I always enjoy a little Mecha Bash-up, my interest is tantalized, I'll see about putting something forth... no promises that my imagination won't go a bit wild though >3>

big question though, what are the important limitations? I see the implication that 'we don't have beam-weapons', apparent from the way the enemy's beam weapons are mentioned, but if we're supposed to be the experimental 'hope for survival' kind of team, 'would' we have such weapons of our own? Salvaged enemy tech? reverse engineered prototypes? Cybernetic augments? Neural link computer bullshittery? things like that? :P