I have a few ideas about builder bots (of any type).
1. A toggle (in engine settings maybe) to choose from one of two behaviors for builders: one where all bots of that type focus on the building that's closest to being done and one where they spread out so that each bot is building it's own thing. In some cases I've found I prefer one way or the other so it would be nice to be able to command the bots.
2. I notice many times where I am attempting to manually force bots into one or the other of the two modes described above that they don't listen. I click the bot and tell it to move to X building but it goes there and builds Y building instead (a neighbor). This happens with large buildings while zoomed in so I know for sure I'm clicking the right one. Example: I may have told all my dig sites to upgrade but they all need artifacts to do so (and I don't have enough). I want all bots to finish one site first before moving to the next one. So I click each one and click the site I want to start with so that the artifacts I do have all go to that one building and get it done instead of having ten that are almost done and having to wait.
3. The ability to summon all bots of a certain type to a tile. Or all idle bots. Example: I've got a bunch of buildings in process but suddenly want them to all stop and build something else right away.
To implement #1 I'm thinking just a priority of total number of all resources still needed and then have the bots pick the lowest number. Usually I don't even care about distance: I'm using this mode mostly when I've told ten things to build but only have the resources to finish one. So no matter how far away, I want the bots to all choose the same site.
The other mode would be too pick the site that has the least number of bots already building it. In a tie, the closest wins. This is when you've told ten things to build and have enough of *most* resources except for one critical one which would hold up construction. Each both could supply the other resources to all the other buildings as needed so you're eventually left with everything done except the one "bottleneck" resource. This is when I'd switch to the other mode so they finish the remaining buildings one at a time. :)