Anyway, I'm also considering a RRS L-bracket for the 5DMKII and was wondering if all of the components (RS-7, L-Bracket and wrist strap, etc.) were gonna play nice. The wrist strap is intended for the 5DMKII.
Not quite, but with one addition - yes. Actually, the three you list (BR strap, RRS L-bracket, and wrist strap) will play nice - the L-bracket has a lower lug for a wrist/hand strap (that's what the camdapter provides), and a threaded socket for the BR FastenR-3 lug. The 'not nice' part is that to mount the L-bracket to a tripod, you've got to unscrew the lug.
The solution is to put an Arca-Swiss type clamp on the BR strap lug. I use a Kirk QRC-1 clamp for that, it's a small 1" clamp (RRS has a 1.5" one, the B2-FAB-F, but a wider clamp isn't needed for this - the Kirk 1" holds even my 1D X +! 600 II). Connect the BR lug to the clamp with a little Loctite Blue 242 on the threads. That way, you can unclamp the strap, mount the camera to a tripod, move the clamp to a lens collar plate, or another body (you could get an RRS base plate or Wimberley P-5 for your Rebel).
Have a good trip!