It is unclear what function you want the list to perform…
A simple list of players you've met seems unnecessary (unless your friends are so numerous that remembering you have 'friended' someone is difficult).
If you are interacting via other [social media?] programs, those tend to have contacts lists (or equivalent), making the addition redundant.
If what you are looking for by way of "keep[ing] up with them in game" is more akin to notifications of activity, this sounds both resource intensive [there would need to be a central clearinghouse] as well as rather invasive.
Rollback Post to RevisionRollBack
WARNING: I have an extemely "grindy" playstyle; YMMV — if this doesn't seem fun to you, mine what you can from it & bin the rest.