As mentioned, scope of (re)work should include inspecting and fixing any water damage in the floor/ceiling from the leak. Which means you’ll have to rip out the existing work.
Another option what about placing a free standing tub (placed underneath the current shower head) instead of building another dedicated shower space? No regrading, tiling, etc after removal of the existing job. And you’ll now have a tub + shower. 2 for 1 and an easier DIY.
I guess this means no peeing in the shower until it’s fixed.
I agree with the others who chose A.
Rip it up. You have no idea what kind of waterproofing/prep is under the tile. If he screwed up the tile that bad, I’m guessing he screwed up the prep and that’s just as/more important than the tile work.
I just took over a half completed project where a contractor was fired. Part of the job was two new bathrooms with curbless tile shower bases on second floor. First floor has a ton of ornate wood working/beams etc on the ceiling below the bathrooms.
The showers weren’t tiled but prepped and I had hesitations about how the prep was done. We ripped it up and found both drain elbows weren’t glued to the drain pipes, the waterproofing membrane wasn’t lapping itself properly etc. Meaning, if we went ahead and tiled it, the first shower would have resulted in water coming down through their very expensive ceiling below on to their very expensive dining room table.
It sucks to take steps backwards but it’s the only way to ensure piece of mind.
I would hire it out, personally. Tile is easy to do poorly and hard to do well. Inexperience can lead to costly mistakes. If it was a kitchen backsplash or something inconsequential I’d say go for it.
I’ve done one myself before. Local code to me and what I found online is how I did it. I was pretty meticulous about sloping the cement poured for the pan. Did the person put the proper impermeable barrier under the pour or support structure? Up the walls? Even then, if something got under the tile/grout it would seep down to that and then slope to the little vent thing in the drain that’s below the main surface.
Both houses we’ve had when I redid something the jack legs just put wall tile right over the drywall. No barrier of any kind. I always use barrier and cement board instead of drywall.
But yeah, code anyway is that you’re supposed to also be able to fill that sucker pre-pour of the base to show the barrier isn’t leaking then after also. Then when you drain it should all drain out.