Whilst hiving off ground handling to a third party can be financially attractive, it does mean that the airline 'loses control' of the ground handling. they become reliant on the third party fulfilling the contract in terms of staff numbers, standard of pax service etc. It's fine to say 'well, if they don't fulfill their part of the contract then we'll get somebody else or withhold payment', but on the day that things go wrong the airline can't do anything about it. For that reason Aurigny (and quite possibly Blue Island) will most likely keep ground handling 'in house'. Whatever some posters may think and say, both companies sell themselves to a large extent on service.
The States of Guernsey have a problem with aviation and it all comes down to 'bums on seats'. They require year-round services to help the economy of the Island, they also need to make sure the 'life-line' routes keep running. That's why they took a financial interest in Aurigny in the first place. However, they can't simply award Aurigny routes and block other airlines from flying on them in order to protect both Aurigny and the life-line routes. A good example was ACI - Jer. Hart told the States(GCI & JER) that there was not enough traffic on the route for one operator, let alone two, and if they allowed Blue Island to operate on it then Aurigny would pull off.... and that's exactly what happened. When Flybe started operating a Manchester-GCI route, it hurt Aurigny quite badly, but again the States is not able to protect them.
There are a number of airlines that operate summer charters to the Islands, because they can make a quick profit at it. There aren't many that would maintain a year-round service. Despite what many post on this forum about wanting/needing new routes to the Island(s), both Islands are actually quite well served in terms of destinations/frequency of service.