The poll on the issue was in favour of the state based system, by 2 to 1. Your suggestion though, would still require people to split up their sightings postings, which defeats the purpose of the incentive of making it easier to report sightings in the one posting.
It is indeed a lack of new product that is limiting the number of sightings being reported, so we may need to see if we get more traffic when new stuff does start appearing.
I can reopen the series based topics for anyone who prefers to use them, but the best compromise I can offer is to have someone else (me if I have the time) to copy new and significant sightings from the all-in-one (convenient) posts, into the separate series topics.