Can we do anything with the abandoned outposts other than destroy them?
Some of them have useful entities and seems a waste...

Heya,

While biters are something you defend against, outposts are something you attack (if you wish).

They have some stuff there, like scrap and also the warehouses and storage things that have goodies. That's their basic loop.

Is there something you have in mind that you are thinking of?

Cheers,

A few I found had laser turrets which I would very much like to steal and move to my own base.
There may be other mods that allow taking over enemy bases, I'll check

Using https://mods.factorio.com/mod/capture works well.
I still need to clear the area, and disconnect laser turrets first, but now gives me more incentive to capture/clear them out.
(I modified it to allow capture of turrets)