Soil pipe simplifying and waste run questions

I'm creating a wet room out of a bathroom. I lifted the floors to find the soil pipe run as in the attached diagrams. Two questions (assuming I can get the required fall)

1) Is this soil pipe arrangement (in yellow) look okay to you? It looks unnecessarily convoluted to me. I think there was previously a toilet where the the end cap is.

2) Do the waste pipe runs (in red) that I intend to put in look okay? They will join the soil pipe with strap on bosses.

I think the soil pipe arrangement is asking for trouble but its been like that for years I presume without probem. I have taken the dead leg off as a start and will put an end cap in there. Doing much more will be tricky as you can see from the limited access shown in the photos.
Any thoughts?

I would seriously remove as many of the bends as possible and definitely the dead leg section if at all possible. You want as short a run as possible, with as few bends as possible, or you'll be inviting trouble. It might be possible to use a 45° bend on the end of the horizontal run to kick the pipe up, then just a 90° to send it under the wall into the next room, (if not, then I'd continue the horizontal run, fit a 90 to come upwards, and then turn the junction round so the WC connection comes in via the branch), and do away with that abortion that's currently there.

Appreciate it has been there for some years, seemingly without problems, but it could prove noisy in use, doesn't look good and every part of my professional mind is screaming it is wrong! Could also be issues with a modern 6 litre flush WC connected.

Shower waste, I'd look at putting a hole through the wall under the floor, and taking the most direct route, again, with the extra bends it is a recipe for problems. If it blocks, every bend is another obstacle to get around, as well as potential to slow the flow down, especially with a fast flowing shower. (Advise you use swept bends rather than the elbows for the above reasons too.)

Thanks Hugh. Sounds like good advice. It certainly didn't look great to me. I have already removed the dead leg, that was easy. I will try your other suggestions. Unfortunately its not as easy in real life as it is on the computer; access is really restricted , but it has to be done.

Make sure any cut ends are suitably chamfered, ensure fittings and spigots are well coated with a decent lubricant, (not washing up liquid!), and the things should go together fairly easily, hopefully make life a little easier. Any problems, come back and ask.

Thanks for all your advice. Incidentally why not washing up liquid?

Your 45degree suggestion appeals. If the angle can't be 45 would you use something like this or would you opt for your other suggestion of a 90 drop? https://www.screwfix.com/p/floplast...L7ljHv0-xptfBSDmvjEaAh6hEALw_wcB&gclsrc=aw.ds

You can use the adjustable bend if required, I dont see an issue. Not the prettiest of things, but hidden under the floorboards, no-one will see it.

Washing up liquid can rot the seals, just use this. https://www.screwfix.com/p/floplast-silicone-spray-40ml/3290f

Many thanks, Hugh, for giving me the advice and prod that I needed. I will fear the soil pipe no more! I've attached not great photos but hopefully you can see that I have followed your suggestion including turning the junction at the bottom of the vent pipe around. I feel much happier now! Cheers. (The last picture is as it was)

Looks a tidy job, nice one.