[Abagail]

If you carefully read my post, you'll know that this can be done without changing your account system to MySQL. Simply create an SQL table with the name of player files and their respective IP addresses so you can SELECT all accounts linked to that IP. Make sure the table is updated when names change, etc.

SQLite is a good platform to use if you do not want to host a full-on SQL server. For more information on the SA-MP implementation of SQLite, check out the following tutorials:
https://sampforum.blast.hk/showthread.php?tid=449536
https://sampforum.blast.hk/showthread.php?tid=262417