What would you do?

I sure wouldn't surrender all that capability for one body and lens. My advice is to not, unless the new camera fits a very specific shooting requirement your current gear does not, as there's a vast range of things the new camera and single lens cannot do that you can, today.

Put another way, does it make sense to trade an 88-key piano for a 24-key piano that sounds rather better in a two-octave range?

Cheers,

Rick