I'm very surprised that none of the smaller sets haven't been re-issued via Direct Service - though I have seen a couple of the Yellow Lady from the Park Fence 5360 set pop up on eBay from some Maltese sellers, which did make me wonder if some little sets were coming for Direct Service.
We've had the various re-issued Cars/Ford-T Trucks, the piano, the lamp post, park fence and the advertising column.
Personally I'd love to see 5503 (Lady with luggage) or 5400 (flower seller) which would be affordable and fill in gaps in lots of people's collections.
I doubt they could revive the mansion of the simply fact that (certainly in the UK) you can easily pick the house up for maybe £150 on eBay with furniture, less if you're willing to hold out. When they stopped making 5300 it was selling for £125 in the shops, so it's hard to see how they could sell it.
What I would personally love to see is a revival with a smaller house/shop - so one room/3 windows wide, with a shop on the ground floor and then a floor and attic above, with a gable rather than a hipped roof. Their could be a range of shop interiors, and it would mostly be recycled moulds, and it would be a different range for them.
I'm sure I read somewhere that they designed a Town Square Fountain for the 1900 range that was never produced, which obviously I'd LOVE to see!