Thunderball,
This is a rumour network, so isn't that what we're here to discuss?
I don't know if the catchment area would be big enough to base 4 or 5 a/c, but I can see some logic in having a smaller presence there:
SOU has capacity constraints & a strong existing presence from Flybe
Ryanair have never expanded on their presence at BOH
BOH has a wealthy population in the surrounding area, who might appreciate those little differences over Ryanair, such as allocated seats.
Reasonable presence of charter flights, but little in the scheduled department beyond the Channel Islands and 3 Ryanair routes