Originally Posted by johnlyons53

The gear shift change won't be much of a problem. You'll need to get new cable stops that attach to where the levers are now. Rivendell or Harris and others have them. Once you do that you can run whatever shifters you want.

You probably could put a brake on the chainstay bridge by drilling a hole and installing a caliper of the correct reach. It's possible that the one on the bike now could be relocated. The problems will be cable location and a casing stop. If you run casing from the hand lever all the way to the brake that will make it easier. There's a reason nobody puts brakes there, though. It will be guarenteed to get all gunged up with grit and crud from the road (especially after a wet ride) and eventually stop working. Not a great idea.

Finally, changing the fork to one that has a different offset (even though it's a straight blade it will still have offset) will greatly affect the handling - maybe better, maybe worse. You'll need to do your research and you should start with Bicycle Quarterly Volume 5 #3. That issue focuses on frame geometry and fork offset, etc. Well worth the $8.