I think removing Pack Howi auto attack to improve the number of shells in the barrage to 6 (with a slight cost decrease) would be an interesting change. It would basically be like a mini LeFH/ML-20 but mobile, or an infantry version of the Priest. This would be both unique and it would decrease overlap between mortar, howi, and scott.
Sounds like an interesting idea but on the other hand should USF have superior infantry then Ostheer and superior support weapons?
Once more the idea of buffing things or cloning units across factions without taking into account factions strengths and weakness is bad.
If pack howitzer has little reason to be built replace it with mortar in the tech tree (no reason for a T0 mortar in the current tech system ) and make it doctrinal.
With the little testing I have I see little reason for USF to actually unlock anything else then LT, Cap, Major and go for the new Dozer which is broken for the price of Sherman+munition or M8a1.
Removing the T0 mortar would may actually force them to unlock it.