One minor/detail thing, which could be "cool":
Playing Far Cry 2 (again) at the moment, sneaking through the jungle, armed with the a bit aged flamethrower from the beginning (well, it is a new game).
If you didn't noticed it yet: The flamethrower in Far Cry 2 is a realy stealthy weapon.
But - back to the flamethrower in general - wouldn't it be a cool detail, if you can ignite and turn it off with a button? I mean the small flame in the muzzle which ignites the combustible in the most flamethrower models.
Also it could be better for sneaking to turn it off, but in this case a player can't react fast; need to ignite it first. If it is ignited, a player could react faster and fire it, but enemies closer to the player could be attracted by it's (idle) sound.
Also a cool ignition animation (with a small rising flame - or something like that) would be a cool detail.
Plus the fact, that it burns a bit of its fuel (ammo) while it is active could be added as an detail, that makes everything regarding the flamethrower more realistic. Even if the ammount of used fuel is realy minor. ... a counter could be useful in this case: like 30.00 --[15 sec later]--> 29.99
If you fire it, it goes down realy fast of course.
P. S.
A bit off topic, but why not bring back a small mobile mortar. Maybe with a better usability similar to the fixed ones in Far Cry 4 (and later)?
(Using a small drone/quadrocopter for aiming combined with a (self-made) aiming module on the mortar ... and maybe homing mortar rounds ?! ... how could they be homing?? - With air brakes like some artillery grenades from a armored howitzer. Also self-made of course.)
And it could also use incendiary ammo ... or other - more exotic - things, too.