It's not a case of the individual aircraft being able to handle the crosswind limits, but of ATC capacity at the airport being reduced due to increased separation for bad weather. If you had 1,000 movements planned at Amsterdam today and ATC can only handle 800 then 200 flights have to be cancelled and regrettably one of them is the Southampton flight.
Going back to the rest of the thread, I'm led to believe that the A320 will have performance limitations at Southampton. It all comes down to runway surface, temperature and QNH as to whether those limitations will be operationally restrictive on any given day for a flight to Alicante, Palma or wherever else. Reducing the height of the trees so that they are no longer limiting obstacles will make the A320 performance restrictions less likely to be encountered than if they remain in place. So (for example) you might have a 20% chance of a performance restriction with the trees which drops to an acceptable 5% chance if the trees are lopped.
And Flybe 3.0? It's beginning to shape up as though Flybe 3.0 is very much in the making, although with a different name (not as green as it sounds) and a different aircraft type (ATR72). It has all the hallmarks of an airline trying to find a gap in the market in need of filling, and the chances of that being profitable are next to nil, from all I can see.