Scawen said it isn't easily remedied. Anyway...
I had an idea for an interim solution, but my InSim tinkering diary is too full at the moment. I thought I'd write the gist here in case anyone with time thinks it's worth a try

- Keep a master list of allowed mods (weighted according to preference)
- Keep an account-based list of nominated mods
When a player joins:
- list the nominated mod of every connected player
- fill the list to 120 from the master list
- set list by MAL
So, there would be a 73+ mods available and shown all the time from a master list of all allowed mods, which can be more than 120.
More importantly, every player could choose their one mod from the master list,
however unpopular, and it would 'just appear' in the mod-list whenever they joined the server. (and the choices of players who have left would be flushed then too).
The only drawback I can see is if player 2 starts using player 1's nominated mod, and then player 1 leaves and player 3 joins - that might cause some hassle for player 2