Wow, this is going to be one lucky hamster. I can't reply to everything, but hope this helps a bit.
I have the Trixie Leif Labyrinth house and I love it. Luna sleeps in one partition, and food storage in another, then she burrows down underneath it all to go to toilet, which makes spot cleaning so easy, just lift the house up when she's not in it.
The things i'm not sure about are hay? I've never scattered hay in Luna's cage, this may just be something I don't know about. She does have houses made out of hay and a maze which she nibbles on.
It's hard to imagine what your set up will be like when finished, but maybe the water needs to be a little nearer where your hamster ends up sleeping.
When I set up a new layout in the cage I always watch Luna to see if I need to move things a round a bit, more often that not I end up tweeking things around.
I think the mouse tunnel may be too small for a syrian, especially if the one you get ends up being on the larger side.
I know people do use them but I don't like suspension/hanging/rope bridge things, hamsters are not as agile as mice/rats because they don't have the longer tail that helps balance, hamsters can fall and hurt themselves more easily, I would prefer to use the other type of bridge you mention
https://www.amazon.com/Niteangel-Sus.../dp/B016GKF250
You may also want to get something a bit bigger for the sand pit, I started off using one of the toilet corner things, but it wasn't really large enough.
I think you are going to be so excited when this all arrives and you get to set it up.