Adfly,
KLM city hopper used to fly from SOU with S f-340's
Air France used to fly 2 or 3 times daily to CDG with ATR-42's
British Airways Regional tried Frankfurt and Munich with ERJ-145's
I think even SABENA operated at some point to BRU with Dash eqp
Aer Aran flew to cork with ATR-72 for a number of seasons before that was stopped
Skybus has also tried and failed with its Twin Otter to Scilly
I don't hold out much hope of the same airlines returning on the very routes that didn't work for them.
However I do agree that BMI regional would be an interesting trial as you mentioned