Not sure if this is actually possible in how your code actually works, so please consider this as 'just an idea'.

I notice when I place down a blueprint in the game mode (as opposed to blueprint lab etc), that immediatly, the delivery requests for all the items in the blueprint are put into the queue. Wires however are not yet up for delivery, but only (I assume) after one of the two entities they connect is placed down. Is it possible to have the wires in the queue right away, and yes, I'm aware this might lead to construction robots hovering and waiting for some item to be delivered by another bot

This is the same as with module delivery. Is this a real waste of time?
It should be possible to do that, but consider the following cases:
- when removing one of the two ghosts, but wires are already delivered - what to do with them? (drop and mark for robot collection or to the inventory)
- once delivered, you can't remove the wires without removing the ghost/entity
- the view could be confusing: Ghosts always show the wires, whether wires are delivered or not. I think it is better now: Wires are not delivered until both ghosts were built

Ah ok, hardly played with modules and wasn't aware that that they behave the same, and yes, you're right, I didn't think of the issues you listed.