Allow robots to "relate" to one another, for example a picker getting items dropped by a lumberjack, a knight defending another robot, etc.

With each step robots become more and more better than TC golems. Really.

P.S. But still not as better as drones(from PneumaticCraft), but getting close.
P.P.S. Turtles does not count, since they're programmable.

XD i saw a really big error in PneumaticCraft Drones. Because they are working step by step they are not as much powerfull as everyone things. Because you can do simply 6 Comands than it is over. And with that you can not do even a automated smelting and fuelsupply in a furnace. Because that require more than 6 steps (step 1 get fuel, step 2 put fuel into furnace, step 4 get Items out of the Chest, step 5 put items into furnace, step 6 put what left overs into the chest, step 7 get items out of the furnaces, step 8 put drops into the chest.) So they are powerfull for 1 simple job. But the thing is more than 1 task at a time is hard because you have to think about everything what could happen! I saw that at the sec where dire showed his automated smelting system! And there is the point if 1 robot can do 1 thing good then he is better than a robot that does 2 things bad.
And i think spacetoad know what he does.

So just use 2 drones for your fuel thing. Or more.
Each BC robot is also capable of only 1 task - thats why @SpaceToad planned this feature - robot relations to easily use more than 1 robot to do things.

Yeah i know -.- Thats why i decided from begining to use old stuff instead of the famous. (Nvm spacetoad about your robots),
But now to robots. You are wrong and right with your sentence. Robots can do one thing at the time. That is true but this 1 task include more tasks. (Picking up robot: Finding EntitieItems, Picking them up, And bring them back home and dump them into a pipe (as i saw in your video @SpaceToad. That is more than one dronetask, and in my Opinien the best variant. it is more powerfull because you know what you get! You can plan with that because the turtle will only do this, Nobody can change it (without changing the whole program) and you can see the weakpoints easier, because robots do simply what you saying them, (drones does that too but the error ist mostly on the player side because they have to say every step). The idea of drones is a good idea but a copy of a copy. Same also with robots but only of themselves (bc robots were already in quarries inclueded) and if we go further into the past we can see that the most mods with entities like that are powercraft from mightypork (awsome coder), with his weasle which is more powerfull than computercrafts turtles/computers. Past is not always better but in that case.... Nope i should stop myself. Sorry for going so much out of the Theme. Anyway cool idea @SpaceToad

You're simplifying too much. For drones pick up items in defined area(and even with item filter) - also one step.

No idea what powercraft was but I don't see how it could be more powerful from turtles since you can program turtles to do anything. I had mine strip mining...

Weasle ist much easier to programm and not so dirty as Lua. Also runs the Weasle much more cleaner than CC computer/turtles

I do not think that adding extra, forced robot relations is necessary. The system will work well enough on its own.