As we all know, the printed range of a weapon is it's "close" range. x2 for medium, x4 for long and x8 for extreme.
Therefore a weapon of say 5.56mmN with a range of 50 would be as follows.
PHP Code:
Close Medium Long Extreme
50 100 200 400
We also know that the bullet doesn't just drop out of the air the moment it hits 401 metres, but can travel several miles further on.
Therefore I would say the energy loss from a supressor isn't really going to have enough of an impact on game mechanics to worry about effecting accuracy. Hitting power on the other hand may be reduced by say -1 to each die of damage.
Dark Conspiracy (and Special Ops I think) state laser sights allow the first three rounds in a phase/turn to be aimed rather than the usual one. From memory it has no effect on quick shots and is only effective to 40 metres.
Flashlights have a much wider beam than a laser. My thoughts are the only real benefit is they let the user keep both hands on their weapon and still see.