Fistful of Lead: Bigger Battles works great for 30-40 models a side. I haven't used vehicles yet (gearing up to use some Clone Wars vehicles), but for everything else I've had no issues.
I've used it to play Clone Wars (with my son, in 32mm scale, 5 man clone squads vs 8 man battledroid squads), the Northern Crusades (Crusaders vs Oesel pagans, with my gaming group), and Samurai (several times, with my gaming group).
We've used mounted, melee, and shooting units.
Personally I like the activation system vs say Hail Caesar or Warmaster style all or nothing turns. The cards can still lead to one side really being up, but you always get to go (assuming it survives). It might be interesting to mix it and Battletech Alphastrike's shooting. Cards to go and affect units, but all shooting happens at the same time.