I think these are fair enough points but I still think OP's original point stands. (At this point it's pretty pie in the sky to think a unit rework will happen). "Medium Tank that's slightly better than stock M4A3 at beating P4s" just isn't a strong selling point.
It is not a strong selling point for the USF but I was responding to claims that the unit is trash and as I pointed the issue is the role of the unit and not with its performance/cost efficiency.
Pre-nerf Mechanized was mostly used for Dodge Truck pressure and Dozer Shermans as far as I can remember. Meanwhile the ROF was the only real thing that made the 76MM somewhat attractive since it made up for the lack of HE shells when you weren't using HVAP (do people even use the HVAP on 76MM?). 76MM needs some semblance of AI perks otherwise you might as well get a Jackson if you want to tame P4s. This is even more true now that Mechanized's power level was nerfed pretty hard is other areas.
According to MMX tool in a static slug fest
76mm has 60.5% chance to beat a PzIV at rage 40 and 78.6% chance to beat with using HVAP
and
76mm has 33.6% chance to beat a PzIV J at rage 40 and 50.9% chance to beat with using HVAP
(the 76mm has even better chance if both units are moving)
(so 76mm is not "
slightly better than stock M4A3 at beating P4s" but much better)
so according to the tool one should be using HVAP...
TL/DR I don't think a slight buff to 76MM's standard shell will put it over the top given how the rest of Mechanized was nerfed if it's going to be one of the main reasons you pick the doctrine.
If there is buff that should simply not be in ROF since the unit fire faster than other medium tanks.
On the other hand USF have access to one of the best TDs in game and 4 different versions of Sherman and making all them useful and balanced is a nightmare.
Currently it seem that Rifle company is a more attractive Commander and unless one buffs 76mm to be more cost efficient than Easy8 that will probably not change.