It would be nice if the game reached a state where I could stop babysitting it and do something else while waiting for money. But even with all ingredients automated, there's never any way to stop machines breaking down.
Even if you want to keep that mechanic in the game, you could do something like adding a repairman upgrade that will repair machines, but he takes like...5-30 seconds? That would at least give you incentive to stick around to keep things running smoothly without completely destroying idle play.
Also, the ability to revert to a previous layout would be nice. I'm pretty sure I have enough room to get a second set of machines running, but my current setup works and I don't want to be forced to rebuild the entire thing from scratch if I fail.