Ya, you can definitely apply to the tile rather than the wall... and
this method works really well if you move slowly and carefully as
there's an open time on thinset before it hardens...and it hardens
fairly quick on the wall compared to the pan.

Remember to seal that grout after it's cured for a while.

Take some pictures and post on a blog when you're done! Sounds like
you could put a great how-to article out there for other DIY'ers.