Shower Waterproofing

Little bit of an unusual situation here. Have a condo that have been remodeling over the years as time permits, but there are many times where stuff gets put on the back burner for months or years. Especially of note, this is the only bathroom in the unit, so down-time is an issue.

Case in point, had a horrible bathroom that was drywal glued to exterior walls, where the inside surface of the wall was terracotta blocks. Ended up reframing everything off the wall, and spraying closed-cell foam and leveling in with the studs. Then proceeded to PL adhesive 3/4" plywood that had 2 coats of West System epoxy rolled on the back before installation, and then two coats on the face side after filling the screw holes with PCWoody, a thickened epoxy filler. A weird way of going abut it I know, but I knew I wasn't going to get back to it for a while, and wanted it at least temporarily surfaceable.

So to sum up, the entire surround including the ceiling has been in use as is for probably 5 years now, with no sign of degradation whatsoever. It looks like the day I did it.

So it's finally time to tile, and after watching many videos (TileCoach / Sal / etc.), I'm of the opinion that I should apply some sort of board (cement / kerdi / HydroBan / etc), for the purpose of moving the wall out to clear the tub lip, and to have a surface that I know will hold the thinset. Don't really know what sticks to epoxy coated plywood. Right now the tub fits exactly in the plywood opening, and the plywood goes all the way down to the floor where it is sealed to the slab. BTW, this is a 90 year old building with a reinforced slab between floors.

If you look at the close-up of the tub/wall interface, you'll see the lip of the tub. My thought is drop the board ( liking the looks of the laticrete hydro ban board or the triton board) on the lip of the tub, and then bring the tile down to 1/8" of the flat surface of the tub, then using a foam backer rod in the recess and siliconing the 1/8" between tub and tile.

If this seems reasonable so far, thought the next step would be to seal the seams and screws with ardex 8+9 and either mesh tape or one of the sealing tapes, and then move on to the tiles.

Questions so far:

Other than the obvious insanity already perpetuated to this point, does this seem like a reasonable approach. If so, few more questions.

Would you press the backer board into silicone beads where they meet the tub and other board intersections, or not worry about it?

Would you screw the board direct to the plywood, or bed it into thinset and then screw it?

Once everything is installed and the corners taped and sealed, would you do a roll-on waterproof (Hydro Ban or Ardex) over everything?

Is there a time limit to how long these waterproofing coats can be exposed before the tile is applied?

I'm sure I have more questions coming, but should probably stop now.

Thanks for any input.