Whilst there are good arguments in favour of protecting airspace around commercial IFR traffic the traffic levels around airports like NIA do not justify permanent class D airspace. I prefer the system in e.g. Germany to protect intermittent IFR arrivals at minor airports.
The airport is protected by class E airspace - this allows VFR traffic entry without prior permission, and without any need to speak on the radio. however, ATC can upgrade the airspace to class F when IFR traffic is about to arrive or depart by making a radio broadcast, after which radio contact is mandatory. By implication all VFR traffic entering the airspace whilst it is class E must maintain a listening watch on the appropriate frequency.
A pity the CAA want to abolish all class E & F airspace.