Base or no base
Does it really matter? The aircraft will be parked overnight at BOH and will fly from BOH to various destinations with passengers going to/from BOH.
When an aircraft has diverted in from SOU due to mist or after hours, Flybe has bussed the passengers to/from SOU easily enough so using the offices and crew from SOU won't be a problem.
Just like BA using crew from LGW/LHR.