With "Clipwrap" I could read the "MTS" files at 50p, exactly what I wanted, but didn't find a way to import MTS (shot at 1080p/50) without rewrapping.
Why not just edit in 50?
You can always cut it down to 24p if you so desire once you've completed your edit.
I routinely shoot at 30p mostly because with graphics and moving still images we get less jerk and studder, then if I really need to go to that 24p look I just transcode the final edit.
I find going down in frame rate isn't a problem, going up is where the issues come from.