The fundamental barrier to a "Windows 11 ROM" is hardware architecture.
While impressive, native performance varies significantly based on the SoC: Windows 11 Rom For Android
Every Android phone has unique components: cameras, fingerprint sensors, GPS, modems, and power management ICs. Windows does not have drivers for these. Writing them would require cooperation from every manufacturer (Samsung, Xiaomi, Google, etc.), which will never happen because they are invested in Android. The fundamental barrier to a "Windows 11 ROM"
Google is now pushing on Windows 11 (now deprecated) and focusing on their own ecosystem. They have zero incentive to help Windows run on Pixel phones. Windows 11 Rom For Android