I found out that the bots ran out of energy too easily, often slows down at the edge of the building area. So I think either better to increase the battery capacity of the bot, or decrease the range of the roboport.

And the bots also reacts by personal roboport's range, I have them in my inventory and when ever I walk over a ghost, the bots will come out and build, even though I don't have the item in my inventory. It keeps generate items with no cost.

sorry my writing isn't good, hope you understand what I mean. And I like this concept, keep up the good work