Well, I checked, and armor 2 is actually slightly lighter than hull 2. So I've notched armor 1 down 40% to be the same mass as hull 1. Still has 10hp, so way better than a solid hull1.
1) Would the docking piece be on the ship or the replacement parts?
If it is on the ship itself, then a clamp would seem to do the job just fine and be reusable.
If it is on the part, then your part would need power and CnC to do the docking. Also, it would tend to result in a small piece of the ship being ripped off while you add the big piece you're adding. There are ways to work around that but with side effects. Getting the clamp to destroy itself while still working would also be tricky.
2) Blocks of material can be unwelded/shattered with a disassembler. A poor man's disassembler can be made with a clamp, chomping off chunks of a block as they collide with the prongs but that takes longer of course.
Attaching any loose parts in a hurry would not happen unless you have a space- or drydock in the same hex to apply them with. Grabbing a loose hull strut with a clamp doesn't tend to be very useful
3) This sounds exactly like a recycler to me
You can charge it from a regular fabber by building parts to recycle.
Small is a relative term of course.
The main limitation of recycling a whole ship is the strict cost limit before you lose a lot of money.
Drydocks make it easy to repair light gunships up to $20k if you designed them compactly.
Spacedocks cover the rest.
Solid rocket boosters aren't physically possible yet, but afterburners could be done as an add-on module for larger thrusters and engines.
Basically, a high thrust very high energy cost tube that can attach to a new type of connector found only on engines.
Can't go making it too easy to stick reactors on and make everything simple boring shapes now
I don't plan to make a reactor that fits inside a hull3.
(Technically you could make your own low efficiency reactor with a light disruptor and three tiles of absorb coating inside that hull3)