Haha, seems we're on a similar wavelength! I, too, have been creating a Musketeer > Corsair & Chemist idea, though quite different than yours. I like the base behind your idea it but I'm afraid with indefinite durations the COR would get a little stale in actual gameplay.

I also wanted to say that instead of tossing out some ideas in order to provide a cooldown for Chemist you could also alter some existing ones. For instance one that increases damage dealt by 10% could instead increase Determination by 30% or something. This way damage is increased but it will also increase healing as well.