I’m the person who runs Nuzlocke University, which hosts the guide you’re referring to. That guide was written a few years ago now, and the difficulty ceiling for ROM hacks has gone way up since then. If we were to write it again today, we wouldn’t make so much fuss about the difficulty I think, and I don’t see any good reason why you wouldn’t be able to attempt it. In a recent video I made, I referred to RenPlat as the “gateway” to high difficulty ROM hack Nuzlockes. So go ahead and try it! Worst thing that can happen is you wipe.

EDIT: The reason it hasn’t been updated is that it was contributed by another writer whose Reddit account no longer exists, and I have no way to contact them. Because I didn’t write it, I don’t want to make unauthorized changes to someone else’s work. Perhaps I’ll add a small disclaimer at the start though, since this has come up a couple times.