I think it would be nice to have stats for my personal use, but I think a stats leaderboard is just not workable without more anti-cheat measures in the game.

And seeing as I like messing with things I can't mess with, mere image-modding is not enough for me; if more stringent measures were taken against cheating, I would want more extensive support for mods. For example, the ability to script your own events, triggers, and etc into the game, which could utilize custom images; this would provide support, limited to what the script could provide, for custom-making puzzles.

It doesn't have to be a lot; I don't have to be able to re-write the whole game. But support for making some tasks of my own would be very nice. One of the first things I would write, if a mod for it didn't exist, is a building task for VV3 that could be 'reset' so that builders could be trained at any time.