Although the idea on itself is nice... there is one big "problem"... the Contactlist-Cleanup in Messenger Plus! list all your... well... people on your contactlist
....
People who aren't on your contactlist aren't listed there, so you couldn't select them in the first place
What you want is a way to see the "Reverse"-list. This list contains all the people that have added you to their contactlist, including the ones you don't have on your contactlist...
Currently this isn't possible in Messenger Plus! and it is btw not so easy to do either, because:
A) The "Reverse"-list is only saved in a cache the first time you log on. This means that it isn't possible to know for sure that the list is correct...
B) The other way of retrieving the list is to use the protocol, but Patchou doesn't want to tamper with the protocol for various reasons...
But maybe there is, for your situation, a kind of a solution. You can use a program named "List Cleaner". Now, there are more listcleaners out there, but this one shows the different lists that are maintainted by Messenger: Contactlist, allowlist and reverselist. It doesn't allow you to copy the list or add the removed contacts again, but you easly see the list though. (Those programs are meant for clearing your list)....
Have have yet to see the ultimate ListCleaner where you can add contacts back, copy lists, (un)block contacts, etc... All the individual listcleaners do only part of that. But you can give some a try though, for more info see
CookieRevised's reply to Contact List Manager