I knitted for years American, as you call it, and switched to Continental and love it. So you can learn to do it a new way. I still know how to knit American and use it for two color knitting. You could certainly switch back and forth from one style to another to rest your wrists. Sounds like a good idea.
When I decided to switch I picked a project that had a lot of stitches, I think it may have been ribbed and forced myself to knit the whole thing Continental. Though it was slow and awkward, by the time I was through I had it down.
Go for it!