There are people on this Planet who can't settle until everything is controlled by what they consider to be the "responsible Few". The terr threat is a gift from Allah for them.
I can't imagine there will be much resistance by the Police for the curtailment or tight control of General and Sport aviation. I remember many years ago at Manch, a group of rozzers (scuffs for you Scousers) being shown round the Tower (I'm not sure if they visited PATCRU as well) and being impressed by the blokes (and blokess) in the Approach room. The visitors were fascinated by the RADAR and the amount of traffic operating outside controlled airspace. They were truly mystified that nobody cared about what the traffic was and what it was doing. I could almost see the mental note taking. Something to do with Police mentality, I believe.
OK, entering into the spirit of fantasy and paranoia; how about, say, a flexwing microlight with a shaped charge IED in the nose? I'm sure any self respecting terr could knock together 100 lb weight of high impulse explosive with some light metal and foam plastic to direct its energy.