TL;DR
Bots shouldn't stop a few meters away from their destination to go charge.What?
For example, a logistics bot is bringing something to me, and it runs out of charge just a tile or two away. I would like it to fly that tiny remaining distance at slow speed, rather than going to charge. I have two proposals:Simple solution: A flat threshold, say ten seconds. If they will reach their destination within ten seconds, then just limp there and charge after. It's not optimal, but it should hide the problem pretty well.
Fancy solution: Estimate how long it will take to go to the charger, charge, and come back, and use that as the threshold.