Depending on the routes for Any%/100% there can be leaderboards for each world. If worked with an auto-splitter they can be done simultaneously during full-game runs, acting as a leaderboard for each segment.
Minigames can also be be added; the site plans to add support for points-based leaderboards in the next large update. I do have a recording of my time for Kartos Kart which isn't that bad but can still be improved.
(unrelated but here's a cover art that fits better with the rest of the site http://imgur.com/a/nqABJ)
the main issue I have with ILs is that, at least with world 1, you can't do it in one trip. idk if you can collect enough in the tower to skip it, get what you need from other worlds and then come back to it and expand it before you enter. even if you can, seems like a pain to have to set up. maybe there is a way to easily back up saves and it actually isnt that bad. the BK games dont have ILs probably for that reason
Rayman 1 does have an IL system that tries to deal with this issue. They have one category that does the level like a full game run would when entering it for the first time, as well as a NG+ version. I do understand that this game is obviously more complex, I just wanted to give an example.
Or maybe just get all pagies that are possible to get with starting skills, in world 1 for example i think its possible to get 20-21 pagies without any skills from other worlds.