3. (easy) Brake upgrade options: TRP Spyre, TRP hy/rd, Avid BB7, Hayes CX5, and/or swapping in some Ashima Ai2 rotors.
So I am guessing Dura Ace 9070 Di2 Hydraulic is out of the budget?
I have used the Avid BB7/BB7 SL, Shimano CX-75, and TRP Spyre SLC with the Ashima Ai2 rotors (~66 grams on average) and based on functionality, ride feel, and ease of install/maintenance, I would favor TPR Spyre SLC first, Shimano CX-75 second, and Avid BB7/BB7 SL as a last resort. Although I have not tried the TRP Hy/Rd, the modulation of hydraulic braking is a plus but with the size of the caliper and added weight penalty, I would still choose the Spyre for CX.