There's 60 more slots than what there was a week ago I believe. Almost 50% increase.
The server seems to be showing some desync issues when full now and again (vehicles/road furntiure throwing themselves about a bit) so I would think, personally, we are at or almost at what the server can take based on the code it is now - so I would think that we should not expect any significant improvements on slots as much as we've seen this week for now until FiveM stops getting stroppy. FiveM can be a bit fragile at times and can do some strange things triggered by unrelated things. The Devs have done a fab job so far to get to where we are.
The queue system is as fair as it's going to get I think. I think if someone had a better queue solution they would have said it by now and we would all be dancing around an open fire celebrating. They could set to particular groups to get priority but most other groups seem to have a good bunch of numbers and adding more to the priority group would only make joining for someone like yourself longer and more tedious. RPUK for as long as I've known it have not wanted to be Pay to Win or have any financial benefit to a members experience so really the "everyone is treated the same" with the exception of those recently disconnected and admins/staff is the best it's going to get.
Dev team as said doing a great job at trimming the fat off previously written code. That could be unnecessary functions in scripts, making them more effecient, or making an SQL query become 1 instead of 3 all helps.
The other issue is the bigger you make the server, the higher it appears on peoples lists. Throw in the fact you don't have to sign up anywhere and can join without whitelisting, applications etc will only encourage players to come along. I think last week on 125 saw at or just short of 100 queing. On current numbers that would only be 50 players, but actually the queue was larger around 70-80 today I think - so more players actively trying to connect.
Everyone is going to be frustrated seeing the slow moving queue, but it's as fair as it's going to get and no immediate options are available; while still considering that there is no point ramping up the players to 200+ if the server's gonna make that experience buggy, problematic or cause the server to spit it's dummy out and refuse to work. If you think you have something in mind someone might not have thought of already then I'm sure the Dev team are open ears, otherwise in the meantime it's unfortunate you must wait in order with everyone else.