Fuselage Editor

I don't know how much is possible in the game. But such a possibility could make instead of a thousand parts that the ship would have 500 of them, which would improve performance.
How many possibilities would fuselage editor give us?
It could look like we would connect different parts like now. Then there could be the option of adding them to something like a subassembly, with the difference that after adding there the game would form a coherent one of them. There would probably be limitations, e.g. only with fuselage it would be possible to create this part. That's how I see it, how about it?