When I saw this thread, I thought it was like Elemental damage as in like damage from hail stones, heavy rain, hurricanes and like even if you touch lava xD But elemental damage is in the OP meant. Huge No. If you want to play a game like that play games like wow.
That's a terrible idea for this game, the napalm boots especially. I think looking at the responses in this thread we can be confident the devs aren't going to go with this.
Like I said, damage types if any should be inherent to the weapon type. A lasgun is a lasgun, a bolter is a bolter. So has it always been, so will it always be while the Adeptus Mechanicus holds sway. An ice lasgun would be tech heresy. Similarly, resistances if any should be inherent to the class/vehicle with only marginal room for improvement to facilitate adopting specialized roles. For example, someone looking to fight vehicles might want to take armor reinforced against explosive damage, but it should only buy them one or two shots of survivability. Just enough to give them a little room for error. Again similarly, I don't want to see laundry lists of special effects at the end of weapons. Again, a lasgun is a lasgun, a bolter is a bolter. Different models might have different fire modes, fire faster/slower, reload faster/slower, be more/less accurate, have different magazine sizes, do more/less damage per shot, but in the end they always do the same thing. No silly things like "curses", "random crits", "self-heal", or other "on-hit effects".
HERESY. SUMMON THE INQUSITION AND THE black templars. (Had to use lower case for significance this time)