That is an interesting take on grenades, and I like that it does limit grenade spamming (to some degree). Although I am dissapointed that it also negates the tactic of double flashing to counter people who are good at turning around as soon as they see a flashbang (ala counter strike).
depends on how the flash mechanic works, in CoD, which they are copying mind you (if only on controls), flashes work irrespective (Brink points) of which direction you are facing and whether or not you are doing "cool midair headshots" (more Brink points).