Replace window with glass block

I guess I don't understand why you wouldn't remove the window, replace with stud wall, and tile that side, with appropriate backing, thus losing the window but gaining a tile wall. You could possibly add a narrow but tall window elsewhere, if there is room. My main concern is - does glass block go with your house's architecture? Much glass block looks either dated or like a design mistake, in my opinion. You could also put a clerestory window high up on the wall... thus getting both light and tile.

Also, you might be able to find non standard tubs, or sort of smallish shower tubs (Kohler?); then there are japanese ofuro's, probably an exotic idea, but interesting.