Well the environment always matters. Even if you ommit the environment entirely then you've created an infinite sight map where snipers can shoot anyone. Map design is the personal challenge of the host, but the weapon creator should design the weapons for an even playing field, assuming the host knows what they are doing.
This argument is kinda moot though because nobody has that level or foresight. If you're hosting a server you should tweak the weapons based on what maps you use. The best example I can think of is if you made a balanced sniper and rocket launcher. But if the host uses these weapons on say, a heavily catwalked map, they'll have to manually debuff the sniper because now the rocket jumper has a whole new dimension of mobility