In pick-up games, I prefer to arrange by scenario more than anything. FSM just doesn't work well unless you're balancing some Tournament style match, with 4-on-5 or some bull like that. Even then it under- or over-values the init sink. :-\
If anyone's really concerned about force size and initiative, BV spreads work well for that. And yes, this does fit into the Combined Arms category so it is on topic. CA tactics FREQUENTLY run into problems with the FSM and limit their effectiveness as a result.
Anyhow, the BV spread states that only units within a certain BV range can be used. For example, the Scorpion Light Tank is 306 BV. If the spread if 1000, no unit (before piloting enhancements) can be over 1306 BV. This means you won't have 4 Assault Mechs + a bunch of 30-BV support vees sinking initiative.
This tends to solve the problem well without sucking the life out of the game and still works within the RP scope of battle.