Thanks for the mod! It looks like a lot of your observations mirror my own.
One of the things I've noticed is how poor of a buy Infantry is. Not only do they die in seconds, they are slow on the Strategic map, slow on the tactical map, and have such a short range that it's rare that they ever get a shot.
Now the real kicker is their price tag. $2 doesnt seem like much, but the $1 upkeep is the killer! That is a 50% upkeep cost! Most other units have about a 25% upkeep cost. So basically you have a slow, weak unit that costs way too much to keep around in the mass numbers necessary to make them at all useful.
What I did for the demo was simply double their HPs. This gives them staying power at least. If you want to err on the conservative side, maybe only increase their HPs by 50%, but honestly I think they can use all the help they can get.
Thanks!