This is a kind of risky thing that involves changing the database directly, but I think what you can do is this:
1) Create a new usergroup (probably by copying the banned group), and note the usergroupid.
2) Do one or more queries to update users' usergroupids to the one you just created, based on whatever criteria you want. Obviously this requires some sql knowledge. But for example, you mentioned email addresses ending in .ru . This should do that:
Code:
UPDATE user SET usergroupid=X WHERE email LIKE '%.ru'
where X is the usergroup id of the new usergroup you created in step 1. Obviously this is the dangerous part. If you make a mistake in the query you could change all users or something bad like that. If you want to try this, make a database backup first.
If you wanted to look over the users before setting a new usergroup, you could do this:
Code:
SELECT username, email FROM user WHERE email LIKE '%.ru'
(Note that the WHERE part is the same as in the UPDATE query).
3) Now you can use Move/Prune users to delete all users in the new group, and all their posts and anything else should be gone as well.
Danger Will Robinson! Use at your own risk. Backup first!