The Place footprints action plugin can place in circle:
- Hierarchicaly linked footprints
- sequentially numbered footprints
You might tale a look there. If it lacks features I am more than willing to accept a PR. But if you want to make your own I can give you a pointer here and there.
As for placing only selected footprints in circle you have to go through all footprints and test each if it is selected. Then there is a question how do you arrange (sort) them. Probably by increasing reference number makes most sense and the first one should be on top.