Mass combat is one of the toughest things to do in RPGs. The idea of having huge armies fight each other is cool, more so in a game about giant robots. Just upscaling the regular rules for smaller skirmishes doesn't work in most games. If you have a hundred NPCs on each side, plus the PCs, the GM would basically be playing solitaire. Not the best of ideas to spend your roleplaying time. BCG has a few ways to help you with this.
On the side of the bad guys you have Squadrons to multiply mook numbers by four, and you could even make a Colossal boss that represents a huge mob of enemies. You're not supposed to be throwing Superbosses with Capstones all over the place, and a Colossus-type wouldn't represent more than a couple dozen enemies anyway, but if you want your PCs to face overwhelming numbers you have the tools to make it work. Just stick to fifty baddies per big battle instead of a hundred.
Allied NPCs are done mostly through Supports and Reinforcements, depending on whether the PCs can give them orders or not. Because of this, Reinforcements are essentially independent Support Upgrades with a few Genre Powers thrown in for good measure. They help the PCs carry the battle without taking up multiple turns to do so. They mostly have offensive buffs and enemy debuffs though, plus a few direct damage abilities, so they are completely useless at keeping the PCs alive. If Reinforcements had their own set of special abilities instead of repurposing Supports and Genre Powers, they would do a much better job of being... Well, Reinforcements.
So we'll make some of those. And while we are at it, maybe we could also give them a way to simulate NPC on NPC combat too. Nothing intricate, but at least have something in case Enemies would like to fire at them instead of the PCs and we don't have to curse those useless NPC allies for losing by default if the PCs have to retreat.
We'll keep the Reinforcement Points and Level system, but we'll touch it up a little. We'll be replacing Support Upgrades and Genre Powers with Reinforcement Powers. Reinforcements would know one Power per Level, having 3 Reinforcement Points to use them per Level. They also recover one spent Reinforcement Point back each Turn, so they can help through the course of the whole fight if they stick to the cheap ones.
Enemies can attack Reinforcements to remove some of their Points. Grunts remove PL+1, Rivals PL+2, and Bosses PL+4. If Reinforcements ever hit 0 RP, they're defeated.
What would Reinforcement Powers do? Well, they'd cover the kind of things you'd expect from friendly NPCs that those
two don't get and we can't really give them. The rest would
mimic the best Supports and Genre Powers for the purpose of
Reinforcements: Granting Aim or Suppression bonuses, dealing flat Damage and restoring Threshold.
For example, here is a thing that wouldn't work for PCs but NPCs should be able to do:
I’ll Grant you Power
Reinforcement Power (1 RP)
Effect: One Ally gains a single Genre Point.
An experimental Overcharger variant with several experimental modes of function to suit potentially any purpose.
This kind of ability is way too situational to be worth GP or MP, but as a bonus given by NPCs it is perfect. These Reinforced Reinforcements solve the current problems with allied NPCs, and they make great buffs to give ad-hoc as Plot Powerups. There's enough variety in Reinforcement Powers that you could theoretically even have a Mecha-less PC to commandeer all the allied forces. It is obviously not as deep as having your own giant robot, but now it is a possible option, and that wasn't really the case before.