I really like the idea of changeable signs. Could work well for quite a few buildings.
That might make for great DS packages too, that could exist out of a sign and all the items needed to turn a building into what the sign says it is.
Like a hotel sign. It could come with six beds, a chamberpot, a small table with two chairs and some food.
Would be nice though if for a new system, the windows could easily be changed between the buildings as well for variation, I am not sure how easy it is for the old western buildings, I only ever got my hands on the old sherrif's office though so I am no expert on them.
Aside from the size they used to use, I would also like to see larger western buildings though. Like a saloon with a stage, piano and upstairs rooms along with a bar and a table or two with chairs.