Bukkit

2 suggestions:

1. Add more auto-purger, like log-purger, but for other plugins data. (For EssentialsX, PermissionEx, WG, Dynmap, playerdata from some worlds, and maybe for WGCustomFlags, which stored in WorldGuard/worlds/world/customFlags.yml to.)
Less data - much better performance! (So it's must be ClearLag feature!)
And would be great, if WG data can be removed with region regeneration. (P.S. without overlapsed rg)

2. Add command, or auto process that can do world regeneration (full, or by radius), with limit of RAM/CPU usage (for prevent huge lags and server down) and without touching WorldGuard regions. And God bless you (and 90% of minecraft adm to!) :]

Remotely similar function of regen world have plugin AutoSaveWorld, but this plugin not cool for the following reasons:
1) ASW don't regen world, he just stopped the server, delete all chunks and then just paste regions schematics to world and all chunks must generated again and again!
2) Huge CPU usage when pasted large numbers of regions.
3) After all of this no one mobs don't save! All animals, villagers, item frame, minecarts, boat, pictures, Armor stands is disappear.
4) Structure regenerate without chests.
5) Villages regenerate without villagers (And i assume, if someone have NPC like from plugin Citizens, they disappear to.)
6) Have many bugs, like when console is lagged after regen and need stop/start server.
7) 1 update per 2 years.

1. I'd rather not make a feature that modifies other plugins (Especially their data).

2. I've actually designed a plugin that restores unclaimed parts of the world for my upcomming factions server. It uses worldguard and factions to check whether or not to clean up chunks. I may release this on spigot sometime in the future.

hope and expect :]