I use a gravekeeper in all my neighborhoods, basically an NPC that I create but never play. They live on an empty lot hidden somewhere on the map, and they own any cemeteries in the neighborhood. When a Sim dies, I leave the grave on whatever lot they died on until their ghost generates. Then I teleport the gravekeeper to the lot and stick the urn into his/her inventory, then “moveobjects” them off the lot. At the end of each rotation, if there’ve been deaths, I send the gravekeeper to the cemetery to place the graves that they’ve collected during that rotation. Since the lot is owned, it saves whenever the gravekeeper visits it, so I can decorate it progressively however I want. The main benefit of doing it this way, though, rather than the in-game “Move This Grave” mechanic, is that the in-game mechanic strips the ghosts of their death color and associated behaviors, making them all white “died of old age” ghosts with no special behaviors. And also no anger, if they were angry ghosts. So, if that’s how you’re moving the graves, that’s why you’re not getting more scaring or any puddles and stuff like that. Using a gravekeeper allows the ghosts to keep their colors/behaviors.
To have ghosts spawn on community lots at all, the visiting Sim(s) must arrive on the community lot before ghosts are scheduled to spawn, which is usually between 8 and 9 PM. If they arrive after “spawn time,” the ghosts will never spawn while they’re there. Also, if you move graves there before the ghost has spawned on the lot they died on, they will never spawn on the community lot. (It seems like you’re aware of this, but I mention it for the benefit of other people who might read this. 🙂 ) To make them behave better (or worse, as the case may be), you will want Cyjon’s Ghost Hack, which alters ghost behavior quite a bit, in good ways. This will generally make them more active and liable to scare, on community lots or otherwise.
As for reaper-related wants…Those generally don’t get filled in my game. I don’t allow Sims to plead with the Reaper. When your time is up, it’s up. 🙂 So, no one gets to “defeat the reaper” (unless they have the genie wish that allows Sims to plead for themselves for a while) or “be saved from death.” For the same reason, I don’t allow resurrection in my game, so those wants don’t get filled, either.