strictly speaking i think it'd be fine to just have a shipping container with padded seats and loads of internal tiedowns. roll off the mech, platoon of dudes jumps out and books it for covered positions to stsrt firing atgms or something. a platoon is probably worth st least one lrm10 or lrm15 in throw weight even if each guy only has like one tube.
for apers work you bring the equivalent of Engineers (FLASH)/Saperi (RPO) and cut throttle for close escort so that you don't get schwackd by srms or something in a city fight/bocage hell dimension
i dont have huge faith in machine gun infantry being able to do anything well enough to be bothered with and tonnage is pretty precious for leg troops, but maybe a mortar platoon or so can be mobile based into position. to pack up and relocate you get back in the box and get towed.
mech joining combat may actually be optional since it pulls double for security and prime mover work.
You know, that sounds like a wonderful idea, and I think you should go and pitch it to those five wobbly individuals in the weird battle armor who just got out of the transport pods hanging on that funny-looking 'mech with its arms on upside-down. I'm sure they will be overjoyed to share their C&C on the concept with you.
