Ok. Try #3.
Here's some ideas I thought of for the game & site.

*Game*

-Spoked wheels similar to the ones visible in the picture below. This wheel would be another "skin" our current car wheels use. Of course they will be resizeable, meaning they can be used on tractors and fancy cars.

-Exhaust/Moufler, Transmission, Brake light.
Exhaust/Mouflers would be attached the same way you add power to wheels. Under options, and select. Why? Well, believe me, that golfcart of yours doesn't sound the same as your Bugatti Veyron. They would be resizeable and can produce different sounds. Smoke will be visible out the end depending on hp.
Transmissions are going to be very helpful to limit your horsepower. Not all cars are a single gear, so that Mack Semi truck isn't made by Tesla with a single gear.
Beacons activated by brakes are self explanatory. I don't need to say much....

It's a plane game, right? Here's plane related:
Cockpit block (actual 1x1x1 block)
Curved cockpit (same size)
Flaps. Same wings as always, just a VTOL input.

Mobile friendly island!
Small island is needed for mobile users. And maybe the PC verison...
Here's some ideas:
-Island #1 would be a wooded place, with hills and lots of trees. There could be a lake in the center. And cabins around it? A dirt road could circle the island, or mix a dirt road and a tarred road into it. Half the island dirt, other half tarred. Locations for the wood island: Water Takeoff, Outskirts dock (small ship yard, similar to the one at Krakabloa), and [name] Final Approach

-Island #2 would feature a tropical theme, or a few micro islands within a small radius. White sandy beaches, palm trees, again a water airport, and maybe if it's larger a dust airfield. If it is a larger island, I'd hope for a road or two. Who knows, maybe add a sunken submarine as a easter egg.

   *Site*

Some of us can agree the original SP logo (or the previous one) is.... More like-able than the current. It's just a bit too colorful and not simple , you know?
Categories! Why spend 5 minutes searching through someones upload list for that special WW2 Spitfire when you could be checking the users categories? The different categories could be placed below the highlighted builds. They would be renameable. Adding a plane to the category is only available by the uploader. Max amount of categories could be 15.
Tags? Put what tags you would want. All I can think of is Railroad.

That's all I have. Thank you for reading....