best workflow to change sequence dimensions after I've locked picture with 2 camera multicam

So I think this comes up for me a fair amount, and might for other people and wondering what the best workflow is.  I've got a 2 camera 4k shoot that I'll eventually be finishing in 1080.   If I drop the 4k multicam into a 1080 sequence, the videos in the multicam window are zoomed in (am I doing something wrong?) so I'm doing my first cut in a 4k sequence.  Then I'd like to change the sequence to 1080 so I can occasionally zoom in and reposition.    Just to make things more complicated, I've applied warpstabilization to one of the cameras fairly frequently.   

The simplest thing is to copy all from the 4k sequence into the 1080 sequence, change the scale on the first clip to 50% and then do a copy and paste attributes to the rest of the timeline...  Guessing I'd need to redo all the warp stabilizers...

Could also do the scale and reposition in the 4k sequence and output and then drop the output into a 1080 sequence, but am guessing there might be some loss of quality...  Not sure anyone would notice it...  The advantage would be in making all the creative decisions (such as they are) in one pass and wouldn't need to redo the warp stabilizers...

Any opinions or other ideas...  

Thanks as always.