Why to produce different versions of an astromech unit at all? Some of them capable to fly, others are not. It just cause maintenance problems.
On this point specifically, it would probably be easier in the long run to produce all astromech droids with the same features. Though my mode of thinking when I brought that up is that there are all types of parts for different budget levels and different levels of sophistication in the equipment. Similar to the situation of buying parts for your car, some parts are designed with the bare minimum of operations in mind, as opposed to being designed with more then the minimum in mind.
Your examples do not support what you are suggesting.
In TESB the reconstruction of C3PO started in a prison cell from wreckage. Were the cell full of spare parts? I don't think so. It continued on the Falcon. Did Solo love C3PO so much to store spare parts on board? I don't think it either.
In RoTJ there was a small commando only. I don't think they carried spare parts instead of more weapons. But, because it was after the battle, they could receive spare parts from the fleet. So it neither supports nor contradicts your thought.
I'll concede they were bad examples for the issue at hand, though just want to point out a few things that may be plausible.
1. ESB - Chewie started fixing C3PO in the cell, that's true, but he only got as far as putting his head on and tinkering with some of the dials and switches on his back and neck. Considering that 3PO was just blown apart, not disintegrated, it was a matter of fixing the wires and parts that attached the extremities to the torso. Parts for the wiring system at least would have been available to R2 from the maintenance stores on the Falcon.
2. ROTJ - It was a flawed example in this case, I retract that comment.
Just want to say though, I am somewhat a newbie at online debateing so i'm learning as I go. Probebly have to watch the films again to refresh my memory on canon.
- Guri_ps12