I recently moded one.
You won’t have much of use for stock driver because stock LED SST-90 is ~3.2V led but requires huge current, not sure but I think about 8A or so and you won’t find worthy replacement LED, you can have much better performances from XHP leds that are 6V so you will need new driver.
One of the problems is that stock driver is e-switch only and you won’t find 6V driver that is e-switch only and starts in OFF position (when you screw down the battery you want LED to be OFF and then when you press e-switch it powers ON and switches modes). I was not able to find 6V driver (for XHP50, XHP70 and MTG2) with this behaviour, they are either meant to be used with standard clicky switch or with both clicky + e-switch. I didn’t want to drill battery pack and add clicky switch (it would be hard but doable, next to battery status button) so I made my peace that I will have to unscrew battery pack every time I want to power it off.
About the LED, because of the unique mounting of sst-90 you will have to do some modification to be able to mount some other LED, you can check out pics in this post
I used FX-30 driver and wanted to use XHP70 with it but ended up using MTG2 because I had one on 25mm mcpcb because that made much easier mounting it under large reflector (stock screw holes for LED also fit perfectly for 25mm noctigon mcpcb) and centering reflector with slightly modified stock centering ring. Reflector hole is less than 20mm so if you want to use standard 20mm mcpcb you will have to sand it down I think about 2mm or so… There are some more modification needed to fit standard mcpcb in there, it’s not straight forward job…