My apologies, maybe I wasn't clear. Right now, if you want to play a certain map, the only way is to call a mapvote. If you pass the vote (which is unlikely), the current game will be canceled and the new map loaded. Most people know this, so they often vote no, so they can keep playing.
Now, what I'm suggesting is a callvote function which would allow you to select the next map to be played. You call a vote to change the next map in rotation, and people would be more likely to vote yes (if they like the map) because there's no risk of canceling the current round.