Your hips are already getting towards the top range of motorists' headlights, and are as high as the top of some sports cars. I wouldn't worry about a few inches difference in the height of your shoulders as far as being visible.
Riding skill and awareness are far more important.
For example, don't pass to the right of right-turning vehicles, or of large vehicles that could be turning right. Witness reports made that Commonwealth Ave accident sound like a classic suicide slot maneuver -- the truck was turning right when the cyclist attempted to pass on its right. The bike lane may have encouraged the rider to think this was safe, but any time you pass to the right of a motorist, you should evaluate whether that motorist might be turning right. Especially if it's a large vehicle with lousy side visibility.
The height of that rider's shoulders wouldn't have made a bit of difference; probably an SUV making the same move would still have been hit.
I'd say take some of the money you were going to spend on upgrades and put it towards a road cycling skills class, CyclingSavvy or LAB. You'll be both safer and faster if you learn good defensive traffic cycling skills.