I already designed one such Infantry counter in my thread about a possible “Power Unit Infantry”:
Note that the Lightbowman is intended to counter the Militia Line which is though to be the main counter of the new Power Infantry unit. That Power Infantry unit is supposed to get some Infantry Armor then so the various already existing Infantry Counters (like Cataphracts, Slingers and Jags) aren’t as effective against that. These counters were designed for the current very low Gold cost militia and not against a more gold-heavy power unit. They would probably totally crush that unit if it doesn’t gets at least a bit of protection. The Lightbowman would still counter that Power Infantry unit, just not as hard as it counters the Militia line.
I made it this way as in my Opinion the current militia line is imo already used up and won’t make a good Power Units because of various design flaws. Including the obvious one of don’t being “iconic” in any way. I think it still can serve well as a nice tool in various Situations and want to keep this property.