Well, turning SS into a "hot" sounds interesting, but I think It won't solve anything. That would encourage spaming even more, I believe. You'd inject them up front hp losses, and while you reg nothing hinders you from shooting. Just shoot, inject 5 SS and shoot , inject 5 SS and so on.
It will make you inflexible too, no chance to react on new situations or change tactics, if you ask me, the famous "BG tank in the middle doing nothing but swallowing SS" will be buffed instead of nerfed.
UNLESS you have future sight, I think this is unpractical too. But maybe some more powerful healing drug that heals over time could be introduced ? Or changed to, let's say stimpacks healing the same amount of HP as Super Stims but slowly over time, That would be nice, they feel so obsolete atm.