A couple of years ago I made the GXF22 which was a 10A linear + FET driver for my Emisar D4 - https://budgetlightforum.com/t/-/57383, and fitted it with four Luxeon Vs. It looks like the newer Emisar / Noctigons are now using the same linear + FET configuration, but I didn't continue any development on that project because it was just... inefficient and I didn't see significant added value over cheap AMC7135 drivers other than the fact that it is PWM-free.
It's possible to make E-switch drivers swappable, but I imagine it would only apply to side-switch flashlights with a separate e-switch board. (I have to say I much prefer side-switches though, much more ergonomic IMO). There just needs to be a few standards which I suppose is challenging...
Personally I prefer a slightly lighter flashlight. I bought a copper FW3C for my Lume1 project and while it does feel nice in the hand, I've wound up not carrying it around much because it's just too heavy in any sort of pocket. Including the battery, the FW3C is 16g heavier than the much larger ZL SC700d with 21700 battery.
Regarding swapping the LED, keep in mind that the driver is configured for 6V. Perhaps you could swap it out for a XHP50.2 but I don't think you're gaining much there for the amount of work. Likewise the 144AM could possibly fit but at the expense of significant loss of thermal performance; best to just design a driver-led-sink assembly specifically for the flashlight. If I manage to get another SC700d for some reason it could be a fun project.