I'll leave this question here: if FRP were to return/stay for whatever reason, how should it work?
Have you considered why they have FRP in first hand?
I'm not against removing FRP but you'll have to completely redesign USF and maybe OKW. I'll only talk for USF and let OKW experts talk for them.
USF is a faction without late game, USF don't have a tank that can stand without infantry.
There is no equivalence to stock panther, brumbar or King Tiger to stay there a bit more taking the charge while you reposition your army around.
In term of doctrinal tank, USF is in the same situation, you only have one single tank on one single doctrine that can soak damage to let you reposition your army.
To end with the tank "side", all your tanks are paper made and all of them are strongly subject to RNG. You can have a M36 be stopped at mid range and still see your shells bounce from any late game tank armor. Panthers are inaccurate on the move, but stopped and at mid range, you're sure to pierce anything you hit from the USF arsenal excepted the pershing.
As USF you also don't have...
You don't have 6men support squads that can also take the charge and hold the line and USF doesn't have conscript to merge your support squad so you don't need to retreat them.
You don't have a half-track that let you reinforce anywhere on the battlefied and you don't have a bunker letting you reinforce on the line.
You don't have an easy access to HMG and Atgun, no you have or an HMG or an ATgun till you unlock all your tiers.
You don't have access to stock rocket artillery or heavy artillery. Your only "stock arty" require a squishy 3men squad, have a really short range and requires sight. And while using your artillery you don't have access to the FRP.
As USF you have.
Strong Riflemen squads, expensive and requiring 2 fuel upgrades and 120 munitions to be fully operative. And if you don't have them on the battefield you can't do shit. People are bitching around grenadiers being weak, but a grenadiers cost 240 and with a unique 60 munitions upgrade becomes better than a RM with also a single upgrade too and also have access to their grenade.
So the Major and FRP is there to support the rifles which in return support your squishy tanks. Lose your RM and the game is over. Remove the FRP = lose your RM = the game is over.
OR, as I say at the begining, you've decided to completely redesign the faction and Relic let you do so. In that case, as I say, I'm not against removing FRP from the game. Just good luck.