limit the amount of accounts a user can create

Hi,
excellent module!
I am using it in conjunction with some e-commence functions so people can buy the ability to add a limited number of memberships to a site.
This module neatly handles the 'batch adding users' and permissions side of things but I tweaked [hacked(sorry)] it a bit to suit my needs and was wondering if there was a better way to implement / share this, perhaps a contrib mod ?

The functionality I added was to: limit the amount of accounts a user can create by adding a new table in the database where the creator user ID and the newly created accounts user ID are stored so you can see who made who. Then, when the mass-add-user form is presented, it firstly gets the users you have added and loads them into a table, then limits the number of entries in the mass-add-user form according to the amount you are allowed to add (userplus_max_add_users) minus the amount you have already add. See screen grab attached.