Sorry so long between replies. I wanted to share some pics of what I ended up doing at my house: https://imgur.com/a/xYgQgup

There are so many different approaches for sure. Using dimple mat on the basement floor with plywood subfloor is a widely accepted practice. I could find no logical reason why taped and sealed dimple mat on the walls wouldn't work as well. I do know since I've done it, my basement is 100 times dryer and more comfortable. This article informed a lot of my decisions. Ihttps://www.greenbuildingadvisor.com/article/carmic-house-taming-a-basement-from-hell

Tracking. How would you keep a wall sandwich like that together? If you use something like furring strips, you'll end up drilling so many holes through the dimple mat into the wall it seems like it defeats the purpose. I did the wall more to hold my dimple mat in place AND give space for an insulation R-value cheaper than using foam.

Don't put any liquid membrane on the inside, I don't think that's ever a good idea and the potential pressure build up will eventually cause it to fail. I'm a huge fan of the dimple matt approach. One side of my basement, the floor is at ground level. I ran dimple matt from that side on the floor, and up the wall on the other side covering the wall that touches the dirt. On the opposite wall where I started the dimple mat at the floor, I just did rigid foam because I didn't need possible water barrier on that wall. For the wall with the dimple mat, frame a 24" OC wall over the dimple mat and fill with rockwool.

Oh sorry, you're right - it is very expensive. I made an assumption based on some of the background in your photos that you could. The Kreg looks like a good in-between. I know whenever I tried to use the circular saw and just a straight edge my cut would always wander. The Kreg looks like it will at least keep the saw close to the track.

Get yourself the Festool track saw and the 108" track, you'll never look back.

Oh that's great to hear. I'm glad it worked out. 👍

Of course! A consultation is always a good idea and worth any money you might pay now to avoid a costly repair down the road. I may also be too cautious because all my tubs are always on second stories or wooden floors and would cause catastrophic damage if something went wrong.

In that case maybe it will work, but I'd still be worried about the shallow or lack of drop from the top of the drain in the tub to the horizontal drain pipe. I do hope it works out for you. Good luck.

Sorry to tell you, but if you use that tub you are absolutely going to have to break up that concrete floor. The entire round base sits on the floor, so there will be no way for the outlet pipe to exit out the side, it will have to drain into a pipe directly below. This is also what your (terrible!) installation instructions tell you to do. The part about using the flexihose in the instructions only might work if the existing drain is still under the opening in the bottom of your tub. From your pictures, it doesn't look like it will be. Breaking up the concrete is not that terrible. Buy or rent a heavy-duty rotary/jack hammer and you can do it yourself. Then, once your new pipe is run, you can fill and patch the concrete floor that is not directly under the tub, and tile as normal. This YouTube video does a fairly good job of showing many of the steps you need to take. https://www.youtube.com/watch?v=rjgurg4Mcnc

Could you? Probably. Ultimately as long as the drain opening in the tub is higher than the outlet pipe for that flat p-trap, it will "work". I would have concern about the volume water going through that flat part and future clogs. It is still going to have to connect over to that pipe coming out of the floor, so I'm not sure how that would look. What is the tub brand and model number? Is it an alcove tub or free standing?

What is the model of the tub you are putting in? You can rebuild that P-trap by cutting the pipe where it comes out of the wall. You would cut it as close to the first fitting as possible and build a new P-trap that meets your needs. Those flexible connectors are fine, but are just meant to give you a little play so the placement of your new P-trap can be a little more forgiving.

EDIT: Missed the part about the center drain. You need to consider getting a different tub with a left-hand drain or breaking out the concrete so you can bring the pipe over to where the drain will be on the center drain tub.