Very interesting - i'm an inch taller than you but nearly twice the weight! ha ha. Back in the good old days it was always Weinmann 500 calipers we'd fit (pretty bog standard fare to be honest, but nothing was lighter - except maybe for some Modolo professional calipers with Ti though bolts). On ebay for less than a tenner probably. Get a special tandem dual cable, and have one brake lever operating both brakes - ditch the other. You could also ditch the front mech, cable and lever - depending on your route just change by hand (getting pretty desperate now I know!). Bottom brackets are pretty heavy - if its got a boron axle maybe a cro-mo one would be lighter? I'm guessing that cup and cone bb's would be lighter than sealed ones? Cut out the mudguard bridge just behind the bb shell (if fitted). What about drilling lightening holes in your derrailier jockey wheels, front mech cage, brake levers (dodgy, but they always used to do it!), chainrings and the larger of the cassette sprockets. Finally, think how much a full spray can weighs compared to an empty one - get some nitromores and get everything stripped back to bare metal
You could get carried away with all this stuff couldn't you!