Idea: Enable players to categorize, organize, and add their friends into Sub-Lists. Much in the same way players can already set up Loadouts and name them accordingly, this would let us add specific friends to lists in order to allow us easier access to invite the right people; in the same way that there's a "Friends" and "Guild" group, underneath that might be "Vanaduke Runners", "Lockdown", etc.
Examples:
"Vanaduke Runners"
"T3 people"
"Shadow Lair peeps"
"Lockdown buddies"
Etc.
Why do this?
As the friend # on your list goes up, it no doubt gets difficult to keep track of everybody in terms of what they run often or what gear they have; it's even worse if you're inviting people for a run and can't remember who is geared up appropriately (and/or people you'd usually invite are offline). This makes it much easier to immediately put people into the right areas, which helps everybody out!
Cost to Economy/OOO:
None. This is a purely aesthetic change/improvement. Of course, a nominal fee for making each new list could be considered (like the in-game mail/attachment system), but this is entirely up to the OOO team.
End Result (TL;DR):
Better organization, fewer accidental or inconvenient invites, and happier playerbase overall.
We could also use an external text program to record names, such as Notepad or Word, delegating names to categories fit to their affiliation to the user.
We could also know our friends better on a personal scale rather than throwing friend invites at random people.
We could also be Smeagol and get the precious.