the real issue is that i cant transportt units so its the worst of the car units, that said its nice for early game combat, but vs teamweapons you're never gonna win head on
I don't suppose this is an issue considering its cost and timing?
In all seriousness, i doubt a reinforcement decrease to 28 would be an serious issue for improving grens(assuming they really need it, imo they are largely fine). Without requiring T4 ofcourse.
One of the main reasons people complain about Grens so much is that midrange isn't their domain with the possible expection of G43 spam. If you aren't any good at setting things up to keep that into account, you'll keep fighting at a disadvantage.
Grens aren't designed around mid- to close ranged combat so any buffs in that regard are not needed. A cheaper reinforcement(2 mp) cost and a slight DPS improvement at long range is thus my suggestion.
I don't see how replacing the howi shells with mortar shells would improve the german offmap artillery. Just lowering the CP/muni cost and somewhat increasing delay between barrages/shells should be enough.