You could make something like the terminator from Nhaler , but make it like an addition , like how u have the connect to any mod peice . And maybe make the dial like ur air flow just twist the cap.
If I didn't explain that so u can picture what I'm picturing in my head someone held me elaborate
I think you are talking about the terminator from notcigs, nhaler has the regulator which just regulates anything higher than 5volts down to 5volts. the terminator from notcigs has a potentiometer that you can adjust the voltage from 3to 7volt or so, no longer made though. I actually have used it on my ggts using stacked imr18350s, it was quite long lol.