So my idea is based off what GTA V servers do, clients like Rage and FiveM allow the servers to add brand new vehicle models to the game that are not default game, If possible this would be a major upgrade for GTA SA RP servers, for example a lot of servers have? multiple law enforcement factions, if we were able to add a bunch of new cars unique to each of those factions instead of having to work with the old default game models, then these factions would look much more professional and easier for the player to tell which agency is which. This idea of course could be for much more then just law enforcement, we could added new civilian vehicles and other government vehicle as well.
as I said above I? don't know how hard it would be to allow completely new vehicles to be added to a server and have those models sync with other players, but if there is any possible way to do this I truly believe it could really change the game for how the role-play servers operate.