Campa SR or Di2, wow what a great question!
If you'd go for Campa, you should perhaps be aware of the fact that you can't fit the Campa over torque crankset to the frame.
In this case you should use another crankset.
If you use Shimano Hollowtech, you'll need those plastic adapters that i think you got along with the frameset?
I will use Rotor 3D+MAS which is not along the very lightest choices, but it will be a bit lighter than Ax/ Engage Pelton crankset.
Personally i would use Campa shifters, cassette, FD and RD. Rotor 3D+ MAS + Q-rings and new EE brakes.
But i would expect it to shift quite close to Shimano DA 9000.