I do like the compact layout - the retaining wall behind the station really works well. I think you've used the space more effectively than I did in my own micro-layout, and I'm sure it will look great when the scenery is all in place.

Those brackets do seem too nice to leave out. Perhaps use them to fix a small flat canopy (e.g. a strip of plastic card) over the ground floor at the front of the station, between the two doors, for passengers to shelter under while waiting to board their train?

I don't think you need to remove the roof: British buildings from the early 19th century often appear to have flat roofs when seen from street level, but they really have pitched roofs hidden by extended walls . For example the L&M's Liverpool Road terminus in Manchester (a notoriously rainy city where a Classical-style flat roof would be a nightmare) looked like this from the street:

but like this from the higher rail level on the viaduct:

There's a nice example of the same architectural screening of "vulgar" pitched roofs in Chris Cox's model of some 1840s London houses at Greyhound Place (again)!

Postscript: looking at the three courses of plain masonry above the windows on Bury's drawing of Crown Street station, I suspect this building had a pitched roof hidden away too.

On wagon chassis, in the past I've simply cut down more modern British 4-wheel wagon chassis to suit the period by removing the brake gear and cutting the sides to reduce the distance between the axle boxes.

But your query reminded me that I want to explore the potential of these Virginia & Truckee ore wagons by Bonanza Models on Shapeways:

The ever-inventive Nigel Hill has been experimenting with the chassis from Bachmann's John Bull DeWitt Clinton stagecoach-like coaches, using plasticard for the bodies:

P.S. Sorry, got my locos mixed up, the coaches actually come with the DeWitt Clinton set!

The coach bodies aren't wasted. Adding H0 cart wheels converts them into horse-drawn road carriages.

I'm afraid Nigel's not on RMWeb. He just gives me permission to show his work on my blog.

BTW you might want to look at Newman Miniatures' website - he doesn't print in 3.5 mm, but does do some L&M items in 00 (and N).