As FBS says, the local infrastructure and road system cannot cope. But then again that will be the same reason (together with its proximity to Southampton) that it won't be viable as an airfield either.
Any facility has a catchment area. If you were to draw a line delineating an area that was within a 30 minute drive of Daedalus you wouldn't have much. It has the Solent to the South, Portsmouth Harbour to the East, and the Hamble River to the West, with the first available crossing at Bursledon. To the North half an hour won't get you far past Fareham on the current roads.
We do need to get awayfrom the idea that an ex-mil airfield accupying 350 acres of real estate makes an ideal GA airfield, it doesn't for a couple of reasons:-
1. It can be converted to a regional airport for CAT and GA will get kicked out, as at Southampton.
2. If kept as a GA airport it will never earn enough income to justify its existence. It's a sad fact that 350 acres of real estate in a location like that is worth a lot of money.
Gosport has no decent routes in or out and the development of this site and the other military sites such as Hasler will fund the infrastructure improvements. I'm not saying I support it, just that it's a fact of life.
Development of Daedalus will be yet more infill into Solent City that is gradually filling up the area between Portsmouth and Southampton.
If you were going to build a GA airfield today the ideal location would be out in the country, near to a main road with few neighbours and a couple of 850 metre runways with the airfield infrastructure in the angle between them, not the MoD standard 3 runway layout with a perimeter track round the outside and the building infrastructure outside it. All we need is a philanthropist with a love of flying and the will to make it work.