One solution would be to kick empty retainers, sure you could put a 999m item on it, but many people dont, and until those people go back to the retainers then it can sit there with nothing selling forever, annoying when people end up "stop playing the game" for a while.

Or put in week resets. Or timers, give retainers maximum of 3 days until they depop, you reset it by going back to them and talking.

Dont need to do much, if only a handful can get depopped on a regular basis it would help until 2.0

I spent about 10 days straight trying to get my retainer up on Gungnir (which btw got its access locked for new chars, just shows how busy it is!) and havent been able to, completely given up now.