One idea I had was adopting the LOTR Strategy Battle Game initiative, turn structure and 1" ZOC's bolted onto Pulp Alley to allow larger games of 30 or 40 figures per side.
Leagues would likely be 1 leader, 2 sidekicks and 1 to 3 super-allies with 2 abilities and maybe a boosted d8 Skill. 40 slots? The balance of the force would be allies, followers and minions. Perks would need to be increased in cost or modified slightly to prevent abuse.
LOTR SBG + Pulp Alley Hybrid Skirmish Turn:
Draw a Fortune card.
Each turn roll for initiative. (Drop PA initiative & activation rules)
Winner moves all figures. (Perilous terrain tests along the way. Rushing figure noted by token as the attacker.)
Loser moves all figures.
Winner shoots using PA mechanics.
Loser shoots.
Simultaneous brawling using PA mechanics.
Loser backs away 1" like LOTR SBG.
Plot point resolution.
Recovery.
Some of the PA Abilities would need modification: hiding, sneaking, spotting, burst rules, and a few of the spells.
It would probably need more, linked plot points with slightly harder challenges such that the player winning initiative early in the game doesn't just claim all the plot points. Defeating sidekicks and leaders might also grant victory points in larger games.