Everything really... Maybe it isn't possible in 1 month, but for sure after 4-5 months most of the stuff should've been covered already. They aren't your small-time DEV team.
1. Selling Cars - This is obvious, if you can buy cars, you should be able to sell them. Like... in any other GT main title ever. There's a lot of people who only want, lets say, 40-50 cars in their garage, some less, some want all, regardless, we are going to be rewarded a lot of prize cars, and some of them we may not like them. If we can't sell them, and just discard them alltogether, it fails the purpose of being a prize in the first place. Plus it would help with the overall game economy. I mean, even if you buy a car but later have no more use for it? Just sell it and buy another, yet we can't even do this.
The best system for this would be to create an online Market/Auction, like ebay for example, where you can put your car for sale for other players to buy it with a fixed price or just auction it and whoever gives the best price for it after X days gets the car. It would certainly make the community come together quite a lot as well. Since this is online, of course you can't just put 1000 cars on sale and overload the servers, you can only put for example 10 cars for sale/auction at once, however, it can be any car, LCD, UCD, Brand Central, Gift car, etc... This would also allow to some extent to circumvent the tedious wait for a specific car in both the UCD and LCD where it may take months to get the car you want.
Alternatively, you can sell your cars, any car, gifted or not, normally for 1/4th of the price like in the past. This for me would be the best way to implement this feature.
2. More single player content - Where to even start? Quite simple... More Missions and Championships. Add the feature of Testing (Top Speed - Acceleration - Drag Times) and Drag Racing which is somehow in the game in the Missions but we can't actually do it Online with other people or even in the single player custom "races". We have the absolute perfect track in SSRX for this and the Testing feature has been in GT since its first game ffs...
We have a lot of car variety but most of them don't even have races where they can be used. Gr.2 races are non-existent, Legendary Race car races the same...
Quite a simple fix really. It just astonishes me how little they add per month.
Championships should've already been part of the major career mode from the start, and I mean real championships, not High Speed Ring normal and reverse crap championships, but actual 5-10 race championships with 10-20 laps each. And at the end of those championships you get a nice payout (As well as for every race) and a prize car in the form of a car for that event related category or the 3-way card slot where you try your luck between 3 cars from that category. To make this even better in terms of grinding, make the prize car winnable every time you retry the championship so that you can also sell it.
While we are at it, increase the stupidly low payouts of custom races and add even more features to it. The potential this has for some players is pretty much infinite types of races.
3. Lobbies - I don't play online that much, most I do is Sport Mode very rarely or the Time Trials, so I can't comment much on this, but as I've heard, not having the ability to save your lobby settings and having to restart the lobby to change tracks is an absolute annoyance. How the hell did they implement this when previous GTs like GT6 and Sport were just fine?
4. Sport Mode - First of all, more than 3 daily races. At least 5. I get massive let downs every time I see the races always being on the same Gr.4/Gr.3 categories. Make it 5 daily races. 1 with no SR/DR updates and only with Road Cars or Gr.B, 1 for Gr.4, 1 for Gr.3, 1 for Gr.2, 1 for Gr.1 and just interchange them weekly, next week for example we have the Gr.4 race having no SR/DR updates while the specific road car race will have.
And, most importantly, the penalty system. The algorithm is all over the place... Sometimes people brake test on a straight right in front of the car behind and the one that gets the penalty is the car behind... Sometimes a guy divebombs on the inside, crashes massively against the car on the outside and sends him into the gravel/barrier, and yet the car that gets that punished... also gets the penalty for some reason when he had the corner and was turning just to make the corner. Other times the guy that does this ridiculous divebomb gets a mere 1.5 to 2 second penalty and the guy that got sent into the barriers goes to last place 10 seconds behind everyone and has his race destroyed.
5. Roulette - Yeah... Needs to go... Alltogether. The very first thing would be to stop with the "animation" of this being a random spin because it isn't. Some prizes in those tickets are just there for display and aren't winnable at all. It's a farce. Make it so that tickets give you your random prize immediately after you click them and not show the stupid nonsensical animation that is, again, nothing more than a farce and a waste of time.
But more importantly... Remove the Engine Swaps, Special Car Parts and Invitations from this system. 3 core new features that come down to RNG, not to mention very bad RNG (among the worst kind I've seen being implemented), instead of them being either obtainable through events of the game or them having their own special dealership.
Make the parts and the engine swaps like the LCD, where you have 5 available at one point in time and it changes 1 of them every 1 day or 2. Heck, anything but this RNG crap. As it was already calculated, it would take DECADES to get those engines and special car parts.
Invitations should work in the same way as RL, you buy X number of cars from that brand and you get the invitation ability to buy a special car from that brand. If realism is all PD is into, then at least make it realistic across the board...
Overall, these should be tickets and not roulettes. And the only thing they should give is credits or the minimal chance for a car. Nothing more. Car Parts for cars we don't care about and that we can just buy on the tuning shop? No thanks... OR, make it so we can sell these parts at least.
6. Physics - MR cars are quite a bit far off from how they should drive and it's incredibly noticeable. All the other cars are fine for a simcade that is GT7.
7. FFB - Yeah, imagine having a game that is closer to a sim than an arcade and having poor FFB support... Another easy fix that somehow... PD has not been fixing at all, or rather, has been doing the exact opposite. I've seen videos with people driving using ONE finger on the wheel with FFB at 100% lol.
Like someone stated, if we didn't had these glitch exploits over the months we had the game, a lot of us would have probably given up entirely on this game.
And after these 7 things are fixed to a reasonable level. Then yes, focus on adding Cars and Tracks and minor bug fixes. Many historical cars that we had in past games that we don't have on this game, or the many new cars released... This is a 2022 game, not a game from 2017...
Silverstone, Monaco, Twin Ring Motegi, Grand Valley Speedway, Midfield Raceway... Give us those tracks that we had in past games.