Project developer here, Windows actually has a x64 compatibility layer now for ARM64 systems in general, so any ARM64 Windows device should be able to run x64 apps (granted the performance penalty is worse than Rosetta since Rosetta relies on Apple SoCs actually implementing small slices of x86 (memory ordering model for instance) which isn't true for any Qualcomm SoC at the moment.)

The problem with x64 on arm64 is no longer if it's possible, but rather the performance penalty. As for whether I'll try to make a Rosetta-like compat layer using the hardware optimizations: not sure yet, I have bigger fish to fry before I get there.