Is there an optimal road size? Like, will they prioritize taking routes through wide roads, rather than the thin roads? If not, could be a cool idea to use. Would allow for a more organized road network (through traffic on the wide road, and only delivery on the narrow roads). Could be done via the tiles. Different tiles denote different road types.

I have noticed that water is not being delivered fast enough. Most of my other depots only need 5-10 drones, where water needs 10-15. The water sources aren't that far away either. I usually build buffers as well.

Having bigger MK2 buildings would be nice as well. At the mid-late game I normally have 4 in/out belts on all of them. With only three spaces, I need to pull from another side for the forth. The MK2 could also be used to request/buffer more that one item. With each side being one of the three items (4 outputs, 3 sides).

The Early Transport Drones mod could be integrated into the mod. However, I did notice you have an option for what the fuel type is. Thinking I may change it to water (without mods that add hydrogen), or hydrogen when I have a mod that can make it. But that would also need them to stop making pollution :P.

A possible alternative to the current system where all the drones are in the requesting depot could be adding a "Dispatch" depot. It would feed all the requests for materials in an area (upgradable?). This way drones aren't sitting there, while another depot is starved. However, I don't know how that would affect game performance.

I dont know if this is a bug, or just me not understanding it. So I wont post it as a bug for now:
When I place a depot reader I dont see a way to get the resources out of the depot. I have tried this on multiple items, including vanilla ones. I mostly wanted to use it to turn it off should a tank or chest be full (so there is no massive buffer in the depot).