Feature suggestion...
I checked out the old ULX 1.X one when I first got ULX.
Though I pretty quickly figured out how to work the users.ini magic, I see many have problems.
A suggestion that might help others is to have it read the users.ini you have already (if users are in it, lets say),
and then have it output a new one, with the user just added + original).
This would best be placed in the ULib folder that users.ini is in to keep things less complicated.
Have it output an actual file (after backup of course)
Also, allow the output of your builder to have a comment after all the info.
When editing my ini with SteamIDs, I always add the nickname of the person I just added.
Useless for adding names now, but handy all the same for comments.