I have some ideas for Mordor infantry that can actually fight upgraded units. First idea---- Buffing the Easterlings(This counts for Soldiers of Rhun and the pikemen of rhun), which is: Giving them 600 health unupgraded, and 900 health, upgraded.. And of course giving them forged blades with Sauron's influence.
(The Easterlings that you can currently summon with the spell book)
Next idea could be fun. What about giving the cirith ungol barracks Cirith ungol swordsmen? They would be like the Orcs Frodo and sam dressed up as, look wise. The thing is, they would not be limited and would cost commandpoints(60+). Their health would be 400, and they could be in a battalion of 15, and they would equal Gondor soldiers in every way. They would also cost 300 resources. This idea is just a way to expand Cirith Ungol a bit more, mainly because their orcs have such a cool look. And I know, Cirith ungol already has swordsmen, the black uruks. It would just make mordor funner to play with more than one cirith orc type, and Cirith ungol would still be a useful building once you've built all 3 of the unit types 3 times. If you don't like the Cirith ungol swordsmen being the same as gondor soldiers, you can just make them free, and equal normal orcs.