My thought process was basically the same as yours, and what I did was to get a nvme ssd, a usb to nvme adapter (because my mobo only had 1 m2 slot and that was occupied), and install endeavour there. It fails sometimes at launch because being connected through USB is not so reliable, but whatever, restart once or twice and it works.
Anyway, I have all my drives mounted (the windows C drive, the extra ssd and the extra big hdd) without issues, all ntfs, games installed in the ntfs drive work flawlessly, no need to reinstall thanks to proton lol. I read, write, and interact with those drives without much though on the fact that they are ntfs.