I've got it working fine for one unit, but I want to select several units together and have them move as a group, without getting in each other's way. My first thought was to pick the closest unit to the destination, make that the leader, and have the others follow. This works, but it's not the best formation tactically as only the first unit can attack anything in front. Also, it doesn't work with command queues: I might tell four units to move but one is busy doing something else and needs to follow later, at which point I have no knowledge of which units were selected together. Anyway, even if the units were not selected together, they still need to play nicely and not cause jams.
My current plan then, is a localised avoidance system whereby any unit can plot a path around nearby obstacles in a cooperative way. But I still have to work out exactly how to do that.