Like your layout.....looks good at the moment with lots of potential
Yes I was planning to motorise the waterwheel. I don't see that as to much of a problem. Famous last words.
However it's the water that has got me thinking. Yeah I could use resin etc for the water but the supply to the wheel is planned to be via a timber leat coming in from the right over the bank and the railway cutting behind the bank barn. Getting the correct 'look' where the water flows onto the moving wheel could be tricky.
Have you thought of using real water ?
Yes....I know that there are lots of problems....basically....
1) You can't scale nature.....but build the waterway to look natural with just a thin layer of water over them and shield with foliage and fences etc so that there is not a clear uninterrupted view of the waterway and the running water will give an impression of 'running water'.
2) Leaks....there will be leakage but with a bit of forward thinking and a plastic 'tray' in the right area under the layout the excess water should not be a major problem.
3) Splashing......there will be some splashing, especially around the waterwheel, so make sure that the modelling in that area is at least 'water resistant'.....using plastic sheet instead of card for the buildings......and water resistant glues for the ground cover. ( the 'yellow' version of 'white' glue )
To provide movement to the water a pump is required.
I would suggest a pump designed for fountains or similar. Pumps for screen washers on motor cars would probably work but not sure how long they would last if left running all the time.
Model the waterway as if you are going to fill it with clear resin complete with underwater details etc but then give it several coats of clear waterproof varnish or resin to stop leakage and the details being washed away.
If you do use real water the waterwheel will not, of course, require a motor, although it may need a brake of some sort to slow it down a bit.
The really good thing is that you can tell your admiring audience that "yes, it is real water"
Hope that this gives you something to think about.