True, the fae or neighbors have always been the most intriguing aspect of the series along with its refreshingly accurate presentation of European Culture and Folklore, so a story which expands on this aspect would no doubt be the most interesting. It would be nice to see something akin to a "farm" or more accurately a "sanctuary" that exists to take in fae that cannot or do not want to live by themselves anymore, which would allow for a large gathering for fae alongside human mages that have taken it upon themselves to watch over them. That, or maybe have fae from other countries cross-over into England, which would open up the possibilities for Chinese spirits and Japanese yokai... though admittedly it might be nice to keep the original series' European charm ^^

Oh, and I'm just a passer-by, so take what I said with a grain of salt >.<