I recommend using gecko. It's been tested on loading times and it works like it's supposed to plus you can use practice codes.
For a glitch or skip you could require an explaination of how to replicate it.
If you really want ILs I suggest making a spreadsheet where people can submit their times. Having every individual level on the speedrun.com leaderboard is just too much work to make and maintain, but an "unofficial" leaderboard that doesn't need video proof should be a lot easier. Make a new forum post about it and I'll pin it for you.
It would be a nightmare to add about 120 more IL leaderboards and maintain them. Unless any of the other mods want to go through that effort it's not happening.
I'm gonna be honest, I don't think the game is active enough to warrant any more categories or a category extensions leaderboard. What I do think what could be a very interesting, fun and active category is if we could somehow remove the downtime, sort of like SMS fast any%. We would need someone to develop that though and I have no idea if it's possible in the first place.
As if the leaderboard wasn't cluttered enough already
Like Spyro said, you're not allowed to pause the timer under any circumstance. Part of the challenge of doing 120 stars is doing it all in one sitting. If you can't do that then the consequence is losing a ton of time.
The thing with all these suggestions is that it probably sounds pretty good in your head, but nobody is actually going to run them. If I wanted to do a marathon run I'd do one that already has a lot of competition instead of some arbitrarily made up category.
Why would you want to bring an entire tent with you on the plane
You might want to ask ukogmonkey if he brings anything you can use, I don't know if he reads these forums.