Well for one thing our PI Ships have been stated by WOG to already be far superior to anything everyone else has and unlike the MK 1 armor they are recent enough that the other races haven't even be able to try to catch up yet. Also in the case of another combat event having the vastly superior armor will up our survival odds. There is also the fact with the Batarian war coming up that they have been trying to catch up and even if their tech doesn't nearly compare to our armor we can expect causualties. If we start production of the armor now we may be able to provide them just enough to provide a massive curbstomp on the ground when the war start, you seem to not realise that most of the war wont be fought in space.
Except that on the ground, the Alliance fields Legionaries, Tigers and whatever else we can give them in the meantime.
The Alliance fields hundreds of thousands Legionaries. The Batarians can only field their homegrown stuff as we didn't sell them Arc Reactors. At most, theirs are powered by Dark Energy reactor we made open source, but even that is doubtful. They also lack all the other stuff developed for the Legionary.
And to get into a ground battle, they have to bypass the fleet in orbit, which will be a tall order when the Pydnas are fielded. If they slip troops in without orbital supremacy, they get bombed/lasered from orbit.
The only thing the Batarians have going for them is strategic depth as they have been starfaring for millenia already. They can afford losses the Alliance can't, but at the same time, they are economically bleeding out. Slavery was never competitive with modern industry in the first place. That they then isolated themselves just hurt them more. So I expect lots of conscripts with reasonably good gear thrown at us.
But those conscripts are also facing the Accipters, which are tough beasts in their own right and faster to produce.
And in case of personal combat, I expect Revy to do the smart thing and run.
Or hide in her underground bunker. We sid build one, didn't we?