If you are out to purchase a carbide masonry bit, you might want to consider a glass/tile bit instead. They are in the area of masonry bits at most hardware stores and are slightly more dinero, but give you a clean hole with less worry or cracking and no tape needed.I would go with drilling and anchoring as well as adhering with silicone. The silicone will adhere the fixture, but still allow you to cleanly remove it if you change it out for another design or if the original gets damaged and needs replaced.

Tundra. I use a PVC liner on a preslope subfloor. Liner encloses the entire curb and base. I have never (30 years) experienced water beyond the tile. No caulk. It's a proven system. Of course the mud system is only as good as the tile job. I may dig up some photo details. CTE. "a liner/pan on the bottom is inferior to waterproofing on the top." I'm waiting on this one. Give it time and the current system will be superceded by the next "perfect system". Folks loved cement board substrate until the common corners opened up and let water in. Current acceptable thinking is "yeah, water is going to get in but there is a "secondary" barrier keeping water from migrating further. Not a satifactory solution for me. I could provide further discussion of what is required to fabricate a good mud job, since not all mud jobs are foolproof, but this is not the appropriate forum to continue. Bottom line is I knew I was going to create a "stir" with my posting to roarah, but posters should know they have choices.

Typically, water valve repair plates are used to cover the damage. But whomever did this job didn't do much to minimize the damage. Water valve repair plate. Here's a good set of instructions. But not easy for a novice. And a real pain if you don't have any spares of the original tiles.

Need help installing a bottle trap for bathroom sink. Pipe that came with the bottle trap is 1-1/4'diameter and the existing PVC pipe is 2" diameter. I need help with what type of adapter/transition piece I need to get that'll work.