To clarify the aluminum chainring bolts I've had eventually popped their top off (of the male piece), usually after several install/uninstall cycles. This ended the serviceable life of the bolt. I never had a problem with power transmission, i.e. I never sheared the bolts.
Cutting the last couple inches of the drops off took 30g off my aluminum bars. I didn't do it for weight but I weighed the ends out of curiosity, plus the scale was right there. Even with heat treated light aluminum bars the weight was similar (3ttt Gimondi). Since those bars are pretty light I imagine cutting a bit off carbon bars would save similar weight.
Have you thought of off-the-bike stuff, like cleats (or specifically cleat hardware)?
For a chain guide thing I'd use one of those thing carbon fiber front der clamps with a bent/welded aluminum thing to position the U shaped piece correctly. If you do it right it might even be adjustable (use alum cable tensioner type things as a left-right barrel adjuster?). If it's aluminum it'll be all of 30 grams or something.
This is the kind of stuff I'd love to be able to work on except for me the extra 40 lbs on the body makes gram searching pointless, plus I don't know how to weld and I don't understand the complexities of mechanical design. For example I like reading bits about when journalists see Contador's bike, how freely everything spins. I've seen this a couple times so I think his bikes are unusually finely honed, or else the mechanic is proud of his work and "lets" the journalists see the results. Obviously other teams want to optimize their bikes as well but for journalists to make a point of writing about it means it is unusual for the journalist to see it.
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"...during the Lance years, being fit became the No. 1 thing. Totally the only thing. It’s a big part of what we do, but fitness is not the only thing. There’s skills, there’s tactics … there’s all kinds of stuff..." Tim Johnson