Randall Munroe has a write-up on a mirrored layout where Caps Lock is the modifier key for the right half: https://blog.xkcd.com/2007/08/14/mirrorboard-a-one-handed-ke...
I recently started trying to learn a one handed layout to give my injured right wrist some rest and have been reasonably happy with the space bar doing double duty. (Tap is space and hold is flip.) Though this isn't something that most keyboards can be configured to do.
So far I'd say the flip style is OKish to learn, but I'm still at a tiny fraction of my normal speed. It will take a lot of dedicated practice for me to be anywhere near as fast.