Are these possible?

Modding for enviroments and maps
for example changing the white terrain snow so its easy to see sat chams?

Modding for Bullets
Catridge that can are a little more shiny and more visible
Bullet holes are paintballs yellow,blue,red etc.
make tracers appear more? change the tracer colours
and flash from guns make it like lasers?

Change attachments look such as the suppressor

What is possible and not? Why is it not?

It should be possible
Im betting bullet holes and such would be a special effect
If it wasnt possible then that means you would have to download those files everytime you start the game
Tracer color could be possible not sure
Tracer rate I believe would require something we cant currently do
Attachment modding is easy

FX attributes
done stuff

Modding for enviroments and maps ~ Only thing you can change on maps is the textures. I've tried custom maps, didn't go well
for example changing the white terrain snow so its easy to see sat chams? ~ textures

Modding for Bullets ~ Possible, mine are ninja stars lol
Catridge that can are a little more shiny and more visible ~ probably somethin to do with textures or RS.rez
Bullet holes are paintballs yellow,blue,red etc. ~ you could probably only do 1 color seeing as this is controlled by textures
make tracers appear more? change the tracer colours ~ I've done it, just make the texture way bigger and change the color to w.e you want
and flash from guns make it like lasers? ~ Would also be texture, although, that being said, its a 2D Image, you wouldn't be able to make it go anywhere.

Change attachments look such as the suppressor ~ Custom model swap

Definatly Possible, Map mods have been made before, but not that much. The other things are a little bit more common, it'll take a hell lotta time outta your day to do all of this though /