The advantage to the PAL over the fishing licence is that due to the process to get a PAL the retards are weeded out, it's a system that is already in place so adapting it to include airosoft isn't that hard and it has airsoft regulated in a more serious manner. The consequences for selling to minors is much more harsh then some BS " airsoft licence ".
As you mentioned...we treat ( or should be...) airsoft like real guns...so why not just complete the process and require PAL's. Having a seperate " airsoft only" licence either in PAL version or otherwise is not going to happen. It isn't plausable let alone in the eyes of the government even realistic.