To be honest, a lot of IABSM (particularly v2) is perfectly compatible with TW&T. I steal scenarios, new cards, vehicle stats, new rules and everything else under the sun for TW&T games. For example, I've been considering running a First Indochina War game using Nowfel Leulliot and Danny O'Hara's excellent
Indochina Ain't Half Hot Mum! setting.
One thing I have been playing around with is not counting every NCO as a Big Man for some armies. The result is one or even two squads in an inexperienced or conscript platoon will need the constant attention of the platoon leader to get anything done. You could even reintroduce the Rally card from IABSM to balance the fewer Big Men, and perhaps add in a "Squad Moves" card that allows only a single squad or team to move without a Big Man present... sort of the ultimate Hesitant Troops card, since it will only come up once every other turn and you will still be very much dependendent on the Big Men to move your force down the battlefield.
There's certainly no need to stick to set lists. The ultimate thing you should be spending your time designing is not the forces, after all, but rather the historical scenario you want to refight.