Though the Game uses the CryEngine I ask myself if it will be possible to set the environment on fire like in Far Cry and how this might be realized i.e. using a burning arrow to set a tree or a stable on fire.
The Option to set things on fire might be also pretty great to use in huge battles to cut troops of their allies.
(1 (and maybe 2)).
Some things can burn in water, but not water itself.