I used to be a big Wine user back when I believed in the potential for a commodity Linux desktop for normal people. These days I can’t for the life of me figure out why someone would want to run games on Wine instead of dual booting to Windows when it’s game time.
Because they don't want to use Windows, period.
You could just virtualize it, dual-booting isn’t even needed. Then create private NAT and only whitelist certain ports and traffic. Hardware assisted virtualization is actually faster in certain cases and workloads than native these days.
You make it sound as if it is trivial to configure the GPU passthrough.
Also, you'll need two graphics adapters for this.
Isn't the 2 GPU requirement just for running native graphics concurrently on both systems? You can still use the Linux host remotely over the network.
edit: here's a receipe: https://github.com/joeknock90/Single-GPU-Passthrough