The areas for shaving grams in bulk are the frame and wheels, so you're at about 1500g each for the frame/fork and wheelset. Beyond that, going with TPU tubes saves you a good chunk over butyl (and even latex). Since you already decided on the drivetrain, it is what it is. Otherwise, there may be a different crankset that could be significantly lighter than the 105. From there, it's marginal savings for each individual component where it might be a dozen to a few dozen grams per component. Not really worth it individually, but those grams do add up. I would think you can easily get it to the 17lb range, but to get it from 17 to 16lbs is not a trivial task - that's a few hundred grams that you aren't likely to gain from changing just one thing.