1) This is an old thread idea, there are several other threads on this, and people have had their steel bikes repaired.
2) If anything, carbon fiber would be easier to repair, since all you need is a sock's worth of tow, and some resin in a few bottles. Depends on the configuration, but it is not difficult to do. If you want to learn some of the possibilities, look at threads on building bamboo bikes. Some of those are held together with hemp twine and epoxy, not even carbon tow. Bamboo is obviously not carbon, but either is a bike and the minimum repair is there in the joints of a bamboo/hemp bike.
3) Fixing frames it is more practical to tack it and splint it than to weld the joint. A lot of welders have the skills, but it is asking a lot of anyone to just run a bead on something they have never seen, and can't even do a practise piece on.
4) Stick is no worse than MIG, and is totally doable. For instructions on how, see my post on roadside welding.
http://www.bikeforums.net/touring/53...k-welding.html