Update:
Every aspect of this now works! 
So I downloaded the latest 6.7 from GitHub with the Prof’s charging style timeout exemption added, and it works perfectly. You can now build a charging bladestyle for your charge plug using Fett’s Mix<BatteryLevel and it will represent the charge state throughout the charging process.
Blade ID is a nice addition to make the saber skip to the correct charge preset, but it isn’t necessary and you can just cycle to the charge preset manually if you want to keep things simple.
What I was surprised about is that the illuminated plug doesn’t appear to affect the charging process. Furthermore it appears to correctly show the state of charge of the battery rather than the voltage level being applied by the charger. I’ve used a style that has the plug pulsing from yellowy-amber to green when the level is low, slowly changing to solid green when it’s charged.
It also doesn’t seem to prevent the battery reaching a full charge. I left it until the charger showed green and the battery returned a voltage of 4.17 volts using SA22C’s battery voltage announcement.
If I had to be ultra picky, I’d like the Mix<BatteryLevel curve to be slightly different as the full charge side of that mix seems to be reached before the battery is absolutely fully charged - but that might just be a question of experimenting with different charge presets.
Sincere thanks again to everyone who helped make this work, particularly, it goes without saying, Fredrik who patiently tolerates my whims when I get these ideas in my head. I am in your debt. 
