As I've been progressing the game I'm wondering if individual levels should have different categories based on the power-ups you have? At the end of each world, those new power-ups change the runs of previous levels. Does anybody else have thoughts on this?

You mean like a category where the power-up given to you at the end of each world can't be used? So in Level 1, no bonuses, but Level 3 only the bonuses you get from betting Level's 1 & 2.

Not necessarily against it, but I'd like to see the currently existing leaderboard filled up being I start adding another subcat no on will run, particularly one that would require you to continuously have to erase the progress on the car and start from the beginning of the game to do level runs.

The big one for me would be a no ball recall ability category. It’s something you can control, as opposed to the speed and jump increases. It also changes how you do a lot of the levels.

I appreciate though that we do still have a lot of spots to fill on the current IL leaderboards.

Hmm, The Ball Recall ability you get after World 1 is just one ability; there's a new ability added after every world. I suppose on every other level after World 1, I assume you could navigate them all without ever hitting the kick button when you don't have the ball.

Not necessarily against it; not going to add anything additional though unless interest in the game picks up significantly. Hopefully other perspective runners will come across this thread before making IL runs for World 1 without realizing that after you complete the world the run changes a lot.