I estimate it would add 15 seconds to the time for the people with the map pack to get a game which is not much. Robot could make it where when you start a game that it searches for other people that have the map pack first. Then, if it can't find a game that way, it puts you with anyone like it does now.
I got Halo Wars the day it came out. I have flaming warthog and honor guard wraith. I even have the general rank and all the achievements. No one can beat that.