Better yet, just Un Nerf the Crystal Lighthouse / Bell Spire.. I went from visiting everyone on the world map and Fellowship daily to just visiting the fellowship. After I get my 3rd chest I have to force myself to do the rest of the fellowship visits
It wouldn't even have to be completely unnerfed.
Just make the CL generate 1 extra chest at lvl 1, and again at 6, 11, 16, 21,26. Combine that with a slight increase of the yield as well and the CL would become more attractive again. And of course, the chests have to be able to be gathered from the app as well, otherwise it doesn't do much good.
By having it generate extra chests after rune-updates it sure would be a considerably more useful AW.
I sold mine off not long after the nerfing, since 3 chests, even at about 10x the worth they held before, was just peanuts to someone who made visits all over the map regularly. The decrease was so huge I felt the space was no longer even close to being worth it.
As for the drop-off in new players, I expect that is at least in part because people are looking for a specific combination of boosted goods.
And another is that one can't chose the starting world. So if you invite a friend to play, he will start a city, abondon that and then start again on the world you are on to join you. Make it possible to start where you want to and you will see some of that disappear.
Of course, creating some extra cities also is a way to earn diamonds. Use all diamonds on your main acount, create a new city on each other world, run through the tutorial and you gain diamonds. Use those, wait a month and your cities will be deleted, then do it again.
Though it only works if your account holds almost no diamonds, it is a way to generate them and papers all other worlds with crappy abandoned cities.
Btw, it really shouldn't be too hard to set up an algorithm that keeps track of activity of all cities that are younger than 2 months and have them erased automatically if there hasn't been activity for more than 6 weeks.