And what would that change?
It would still be about guns and killing each other.
The only real way to fix this is to find the source. They need to not be hosted by 10 year-olds thinking that all they need is the cash mod, and a gun shop to have an RPG. As I'm sure you've experienced, they can be horrendously lame and uninteresting. If someone is like me, they check on RPG servers to see whose hosting, what theme and then they judge what they can expect. An ideal RPG consists of a good admin with experience, descent builds and a dash of talent. I do realize that games like GTA and GMod have older and more mature players, but I think that the same feeling can be brought to Blockland, just a little more effort is needed.
If the person is serious enough, they'll stay on the server. If the person isn't as inclined to do a little pretending, and they don't see "Wer can i get sum gunz" in the chat box, then they leave, and I won't have to deal with them. The RP names would really spruce up Role Playing, as the more serious would see that there's no Bullstuff going on (That is, if there are people who are interested in RPing.).