Maverick, if Flybe went belly up then im sure BAA would find someone else to fill the slots at SOU. Im sure Easyjet amongst others would be glad of a foothold at Flybe International Airport, oops, sorry i meant SOU.
I may be wrong (and very happy to be corrected) but I'm pretty sure that there are only 3 or 4 stands at SOU that can house aircraft the size of the A319 at the same time. A large number of stands may be out of use due to the proximity of the stands to the runway. Oh and of course, they'd probably be performance restricted of the short runway, and they'd cut the frequencies drastically due to the increase in capacity.
I'm not sure that SOU would be any better off...ask IOM how reliable EZY are given that they've cancelled their sole LGWIOM rotation each day for the last 3 days running....