The MacPro alternative is very expensive as well. I would need to keep a laptop unless I mount a handle on the Mac display for easy carrying 🙂
Benefit of the MacPro: more cores, more memory,...
Windows PC laptop with external GPU seems like a double compromise ... I don't mind working on a Win machine but hate to have to 'fix/tweak/clean' it regularly and I would still have the burden of an external device.
Not sure at this point but I share your concern. If something pops up, I'll let you know.