A few handy things would be a zeroeth order checkpoint that needs to be crossed but in no particular order, and if crossed checkpoints changed color, dulled, or otherwise displaying that they've been crossed.
I've seen on previous posts that you don't want to make your game a track mania copy, but I think potentially adding difference between surfaces could add a lot more to the game. For example, the dirt could slide more. Also the addition of slanted curve pieces, like a 45 degree bank would be nice. I hope you still plan on updating the game.
There could be a way to make teams or Clubs. In those Clubs you share the Code and people can join.
Like this there could be a tab at every track where you can see the times of other people in the club. So u can race against friends without having to make own maps. There also could be a limit to how many people can join (10 or sth like that). Also could there be a feature where everybody in the club can select 5 (just an example number) maps and now they will be displayed under the standard tracks. Now there is for every member a track which fits there skill.
Your car can keep grip on the track, even when sideways... You could possibly patch it out and make it work for only a specific range of blocks as a feature though
The track below demonstrates this with the different blocks in the game
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Editor copy paste. Like using a special block to mark 3 corners of a cube and press copy and then paste as one big block somewhere on the map. It would be REALLY helpful when building big containers but only having to build one side before copy paste. Also it would be much easier building like lakes or oceans when you need to switch the rotation all the time.
Thanks :)