I think the powers that be know about the road links very well, but it's Christchurch and Dorset Councils fault not Bournemouth Airport['s. So many surveys have been carried out along those roads and it's been proven that much of the traffic is non-airport. The roads are a convenient cut through for Poole to Christchurch traffic and vise-versa.
So if Ryanair pull out, someone will step in or build up. The very fact that Ryanair had two aircraft based at Bournemouth was probably a contributing factor that other airlines stayed away. Even the doom-mongers cannot ignore the fact that Ryanair had some very good loads and there's a market to fly from Bournemouth.
So don't write off Bournemouth because Ryanair may be pulling, out the senior staff may be down to announce more based aircraft, let's wait a while and all will be revealed.
PT