I'd like a high performance alternator similar to one of these. Is it possible to rebuild a stock alternator to similar output, using majority of tools one would have at a home garage? Of course one or two specialty tools might be involved, but if it's pheasible to diy and 25-50% off the cost then it seems almost worth it.
Disclaimer: This isn’t a qualified answer, but I thought it could be useful addition above that of a comment.
I’ve looked into DIY coil repair before, and while such operation is possible (including winding the coils taut using hand drill or bench press), it’s not advisable for a novice. Beside the difficulty of producing a decent coil, even more so difficult is to ensure the sealing and/or insulation of the coil. As far as failures go, that would appear the primary cause in the first place, and a shade-tree mechanic without proper knowledge of electrical engineering and manufacturing practices is not likely to succeed (I’ve read of people’s repaired stators shorting out in several months).
However people do repair automotive coils (generators, ignition etc.), and do rewind them for higher output. It could be advisable to find a specialist either locally, or over the Internet (you’d have to send the device for them to rewind which incurs additional cost).
Well if you have the expertise to rebuilt the entire winding and replace worn out bushes, then yes, it can be termed as a DIY project. However many people are not well versed with electrical motor winding and you may need an experts help. Before you do that, you may refer to automotix.net/autorepair/diy/ which has many DIY technique on repairing and serving motors and engines of several models. This should help in making your DIY project successful.