All the healing methods save for UKF seem pretty proportionate to me.
USF: 250 MP, 10 FU
UKF: 30 MU on a unit that you will always have (granted it costs field presence to use by putting the squad out of the fight)
SU: 250 MP
Wehr: 150 MP, 60 MU
OKW: 100 MP, 15 FU
OKW Medical Supplies could probably still use a cost boost though.
100 mp + 15 fuel is reasonable if you look at it as is, but the point I am raising is that the combined cost of the truck + tier 1 + side grade + "the cost of going tier I instead of tier II" makes that decision more expensive.
It would be like locking USSR field hospital behind tier 1.
Totally agree with you about medical supply though. If the cost is a bit lower rather than a consistent bleed of ammo, it will be better.