I agree with the above, right now I find myself destroying the hospital buildings and putting something else there, and the implants button is just a tease for me as well. For right now, Id rather save the money spent on the hospitals and medics and just hire another soldier when one dies.
But I do like the idea, maybe if healing was instantaneous instead, and the implants were more of a temporary enhancement, like sterroids. Then there can be certain types of enhancements, such as accuracy, speed, etc.
In fact I just got a starcraft idea in my head, and give the soldiers in the mission some stimpacks to give them a boost of TUs for a round or two with the loss of some valuable health. Of course the above would have to be researchable, but it would be a nice fun feature to have.