What you said makes a lot of sense, but i dont think giving it the ability that i said would make the original health buff useless, just because of the fact that no matter what, the original buff is INSTANT full health with pips, and not health over time. And besides, I wouldn't mind having metabolism slightly better than the original health buff, because everyone has the original health buff without putting any poiints into medic, while you actually have to put points into medic to get metabolism, therefore, it would be okay for it to have a slightly better purpose than the original health buff, imo anyway.
And by the way, just as a side note, I worry about keeping players alive more than reviving them when they are down. (but obviously still do both)
Yeah... Like I said, Light characters (imo as a fairly experienced one) benefit FAR more from extra health than from better regen.
Your suggestion would probably make Heavies OP, because they'd be able to hide and regen quickly to a RIDICULOUS amount of health - as it stands, if they take a bit of a beating, they can recover faster with Metabolism, and step out mostly-healed, but you can chip away at them to a point before being forced to rush them in cover when you're weakened too. if you know every time they hide, they're going to come out completely untouched, you're going to be forced to rush them and hope for the best. Even Medium vs. Light will be able to do this at range. it would slow down gameplay MASSIVELY, and shift the advantage in favour of larger bodies with more health.
Heavies already get more of an advantage from metabolism than Lights and Mediums are in between - which is fine, and in a sense, Lights gain more from Health Buffs, which balances it - this would unbalance it in favour of Heavies.
Again, this is just my perspective, but I think there's a reason SD did what they did, and I think my suggested fix would be more balanced.