NOC-BHX ran last summer alongside the extra ORK frequencies. I don't see why SEN would fail if daily, WAT was double daily. Surely the bigger population etc could sustain it.
Population is not the problem its people don't want to fly to SEN so prices will have to be very low to get people there. The SEN-BFS services is failing and when I flew it a few weeks ago it was full of people who wanted cheap flights not because they wanted to fly from SEN and cheap and Aer Lingus don't go.