Well, considering the only gametype coming back that doesn't require maps to take advantage of it is TDM, then the purpose of it, would be something different late in the games life.
3 Team DOM didn't even catch on until way late in UT's life, and the only thing keeping variations like this from happening more often is the competative TDM community and their purist attitudes IMO.
I think 3 team TDM would be a really cool pub game, now especially that the engine is handling larger player counts better. It's also an excuse for more FFA model customization.
No, it doesn't have many uses to implement, but how hard would it really be to include?