Cant understand why you think soviets have best healing option.
Because it only costs manpower and once you build it you never have to think about it again. It can't be destroyed or killed either (Well maybe they can kill the medics?) since it's tied to the HQ. The ambulance in particular is vulnerable to being sniped by something like say a Puma after a mass retreat. Likewise, I'm in the habit of sneaking my AEC into my opponents base when he is elsewhere on the map to kill his med bunker before peacing out. (Works best on a big map.) I think the other races certainly have more potent healing options, but the complete passivity of the soviet option is kind of nice sometimes.
Anyway that's just my opinion. I think the ambulance is most powerful, but it's also the most fragile.
I would argue that brits have the best healing in the game and whilst this is a short fall and can be irritating in the late game its more then balanced out by the fact that it is super strong and effectively super cheap.
I definitely agree, which is why I'm wary of adding anything new especially before late stages of the game. I just think the medics are already there, they're just locked to one doctrine for whatever reason even though they're not a core component of it. I think they'd be a nice quality of life purchase at that point in the game.