In over 2500 hours of playing I have never run out of med kits and only bought them once for the achievement. The current heal timer is sufficient, there isn't any reason to have an inventory item too.
Plus in most game modes you get med kits far faster than you could use them up if you constantly hit the heal button every time it came back on. Interesting the areas where you actually use med kits are where they drop incredibly fast.
Thus you have two choices... Set up auto collect or have med kits strewn everywhere. If you auto collect then you have to remember to drop stacks of 200 that are wasting inventory space. Just a nuisance task for no reason.