They'll have years possibly decades of stored Hexi blocks to use up first!
Squaddies will always end up chucking new kit and using what actually works, When I was in the TA we were issued Heximine. Some of the guys bought other stoves like gaz or multifuel but the majority were happy to use the issue hexi.
one of the delights of hexi is you can make a much bigger burner, on one of our HQ's in a house on STANTA (training area in Norfolk) we had 3 or four hexis in a row, you could get a pile of hexi blocks burning and make a sort of cooking range!. With a little organising you could heat four or more messtins boiling water or cooking at once for a massive brew up, all looked after by one person whilst others cleaned or prepared kit.
Yes, obviously there were fumes but Houses on training areas have lots of purpose built bomb damaged brickwork and holes to poke your rifle out of so training area buildings always had good ventilation.
I can't see that sort of group brew-up happening with the smaller Esbit stoves and fuel.
As they say, "If it ain't broke, don't fix it!"
As for the waterbottle flap question?
I always put steritabs in the tiny lid pocket and milbank in the sleeve
some other water bottle bits.
In 1944" water bottle pouches I agree there is a pocket to carry a millbank and a tiny pocket at the bottom to hold a bottle or packet of water tablets.
in the 1958" pouch you could only carry a water bottle plastic mug and water tablets, nothing else.
US Waterbottles are fluffy on the inside and are designed to be soaked, as the water dried it cools the water bottle! good idea!
FYI Squaddie often carried the waterbottle upside down so it was easier to get out!
