i see, that sounds interesting! :) let me know if it works out / if you have something presentable.
i honestly think we don't need a pull request for these changes. you can download the repo and adjust the tool / game to your needs (the game is basically the bundled code of the tool anyway), but the changes you want a pretty specific. things like "callbacks" are also not really necessary as there are already dedicated functions for checkpoints, death and other things you mentioned. there is no need to make an extra function inside an extra function.