spikeair - it's historical from when Jersey as a very busy airport and popular holiday destination for the bucket and spade brigade.
Quite a lot of work was done to a few years ago to look at changing and bringing in more class D but that was scuppered due to proposed EASA single sky changes. I understand it's back on the radar and being looked at again, however personally I don't think it's going to come in particularly soon and other changes around 2012 may also affect IMCR use
One of my concerns with getting a class D up to say 3000 or 3500 with Class A above it would be that you would not longer be able to get SVFR into the class A and I really don't like being below 3000 over the sea heading North to the UK - I like to get up high and then go east or west of R41