bit late here - like a year rofl.
I never minded the horns if I'm honest - that would mean I hate tieflings as well and I don't. It was the eyes changing I disliked the most about that transformation. Windows to the soul and all that.
Thankfully there is a mod on the Nexus that allows you to either remove the transformation entirely or allow it but keep his human eye - which was the option I went for. Its called Wyll's Mirror by Anshela. it works on patch 8, I tried it on my last playthrough.
Of course neither the game or Wyll himself recognises that he looks human or has human eyes instead of what Mizora is supposed to have changed him into - but you can't have everything I guess, that would be the same if you used consol commands as well.
