Bukkit

What is the enhancement in mind? How should it look and feel?

You should add the clean-old-protections config section to the config help page.

Please provide any additional information below.

That's it.

I would prefer a command based clean up like ProtectionStones offers. But if possible something that regenerates old protectiones slower or asynchronous so it would crash the server :P

Yes you could use the command multiple times like
/ps region regen 30
/ps region regen 29
/ps region regen 28
/ps region regen 27
and so on, but after a couple of times the server cannot take it any further and stops itself.

AsyncWorldEdit also can not catch all regens at once and will lose a lot of them.

@Krauti2: Go

I'm not understanding you at all. What functionality from ProtectionStones are you talking about? Could you please elaborate?

Regarding asynchronous let this part to me, I'm an expert game developer and I know what must be implemented asynchronously and what not.

As you probably know ProtectionStones supports clearing orphaned protections by providing a) a number of days a player has to be inactive and b) an option how to remove them: either remove the WG region only or remove and regenerate it.

Regenerating a lot of orphaned regions consumes lots of resources and at a point the server, even running on a dedicated, can't keep up and CB/Spigot will restart.

Pretty much the same feature for Libelula Protection Blocks, but with less use of resources and running more smooth if possible.

Regarding asynchronous, that wasn't meant to criticize you in any way as this is not even implemented yet ;)

@Krauti2: Go

I agree and I will implement this functionality too.

A quite periodic problem for me is the deletion of inactive protections.
Background: On first join users get a protection block to create their first property for free and need to buy or collect further protection blocks to expand their property.

The problem is when a player is inactive for a couple of weeks all his protections will be removed and he needs to ask for a new first protection block to start over again.

So it would be nice if the plugin somehow would "remember" that a specific player has had specific protections removed to give him the opportunity to re-get his previously bought protection blocks.

It would be also possible to force these blocks into his inventory or enderchest while offline but this would require NMS which you probably don't wanna use as it would break compatibility through version changes.

Best regards
Krauti