Regardless of battery type, be certain that it has sufficient storage (amp hour rating) to support your bikes needs. The stock bike was 12aH, and most Anti-Gravity units are much smaller. They can work, but your bike has anemic charging characteristics. Meaning, the system is in a deficit when the motor is spinning at less than 2,500 RPMs. Stop and go traffic at night will drain your battery. Electric starts draw a lot of reserve power from the battery.
Updating the Regulator/Rectifier only helps with recharging a lithium/modern AGM type of battery, but doesn’t overcome the basic charging profile of the alternator. Things to understand as you proceed…
The mUnit is nothing more than a deluxe fuse block. It has nothing to do with charging, battery storage, or recharging habits. I love them, recommend them, have heaps of experience with them. But, your foundation (charging/battery/wiring) must be in proper order for them to behave. As you are re-wiring from scratch it can be a good choice. All your connections and splices need to be clean, water tight, and securely fastened. Else, you will suffer intermittent issues.