I'd love to see the ability to add entirely new moves, items, pokemon, etc. with their own sprites using server mods.
Another very important addition would be the ability for server owners to add new formats with their own banlists, clauses, mods, etc. without having to replace an existing one.
[15:13:52] <&Zarel> Dusk209, you lied to me so much :(
[15:14:47] <%Dusk209> Is there anything I can do to make up for my sins
[15:15:42] <&Zarel> Dusk209, I accept blowjobs