The RTV system is fine. I do have a suggestion for voting in general:
Instead of 1,2,3,4 use F1,F2,F3,F4. The problem with using numbers is that many people use these binds for weapons and hit them on accident. So not only do they not get the weapon they need at that critical moment, they accidentally vote for a map they hate. Also, many people randomly hit a button just to get the menu off their precious monitor space. It would be nice to have an "abstain" option as well.
I've seen the F1 system used on TF2 servers and it works great.
