That's fun! I think there is a good potential here :)
In my opinion, the 1 thing that would greatly improve the game design is to have the balls give incrementally and significantly more money for each different gate they passed through.
- That would greatly encourage players to try and design incrementally complex paths to really optimize their gains; currently having two short paths might give 1/3 of what a really long path would give, which is not a big difference. With that, a long path could litterally gives 1000 times more.
- The various costs would have a far stronger scaling, so that in order to progress you do need to make those complex paths.
- This way, the player has to stay active and work on the paths; being idle might unlock a thing or two, but an hour of idle gains will quickly be dwarfed by five more minutes with a better path going through two more gates.
- Overall, I think this would allow for a really nice "incremental" feeling (whereas right now it's more idle), with big numbers, and the joy of passing various caps where your output suddenly grows far higher than it previously was.
Just my two cents obviously :D If you want to discuss specifically incremental design, let me know!