Given that the original XML was overdriven to 7A successfully, I’m guessing the mtg2 and xml2 would be able to be driven just a bit more (on copper of course or water cooled).
But I wouldn’t be surprised to see someone overdriving an mtg2 upwards of 5A.
3A at 6v is double the wattage of 3A at 3v. MTG2 tailcap current will double and runtime halve. My S1100 mutant still does over one hour continuous on high, long before the cells go flat you'll be searching for some welding gloves if you want to be able to hold the thing anyway.
That will be about 70 to 80 watt? And active cooling using fan to have less weight. And 9x18650. I think it should be about 2kg in weight. That will be brighter than most HID.
I found out by checking out this light that there is a retail store less then 2 hours away that has many chinese flashlights for sale, planning road trip…
Seriously, I live at least 30 minutes from Going Gear and it is definitely worth the trip at least once. They have just about every flashlight you can think of and they are out where you can try them out (on tethers).