Ozzy Osbourne Let me predictably seperate the points out.
MAN-SOU as a daily service operated at x times per day was predicated on high price business travel to make that pay, that's showing no sign of returning to the same level. Hence you might manage to make a once daily rotation on a prop work BUT that's going to have to be at a relatively high price point AND you need 2-3 other rotations for your aircraft out of MAN or SOU. That 1st airframe needs to be kept flying and the obvious candidates out of both airports have an incumbent. Core point being I see no gap in the market that you can monetise linking the niche, unserved routes together profitably.
My point about MAN was it had (ISTBC) the biggest domestic network of all, and that's not coming back as the market has changed. It's not a lack of an airline, it's a lack of enough profitable routes to make a base worthwhile. "Students, leisure and cruise passengers" aren't going to willing to pay enough money to counter the lack of eye watering business fares that used to offset leisure as a cross subsidy to make the flight profitable IMHO.
Let's test it. What's a solid case for a 4 sector day out of MAN or SOU without getting into a fight with an incumbent? In February.....?