EMX used their 37 seat 200 series on LCY towards the end so a 33 seat Saab wouldn't be a big loss of capacity. It could easily provide 4000 seats per month which would be enough to meet historical demand.
From what has been reported locally, the IOM Govt. would jump at a Loganair option - more likely the problem is at LCY around slots for smaller a/c.
Also, would FlyBe be happy with Loganair flying the FlyBE brand to LCY in direct competition with their own IOM-LGW flights, which is where most business traffic must be now.
Maybe if the IOM Govt want to enhance the London travel experience for business people, they could try to persuade FlyBe to upgrade LGW to the EMB-195?
That said, having 3 identical Q400's based at Ronaldsway seems to give FlyBe more day to day operational flexibility than any of their recent predecessors enjoyed, and they might be reluctant to lose that, regardless of the capacity and image benefits a 195 would bring.