Point blank (+20 or +30) = 5m
Medium Range (+0) = Weapon's Range
Long Range (-10 or -20) = Weapon's Range x 2
You lose out on short range in this case, but I feel like it's a pretty healthy compromise. Also involves no annoying on the fly math. I'm sure we can all double pretty easily.
This is simple and effective. If range modifiers are needed at all, then this is the way to do it.
Agreed.
I'd make it +20/-20, both to avoid the extreme +30 bonus, and to make the numbers consistent.