I’d actually think that going to two lances would more than double match time, especially for inexperienced players. Human beings take longer to make decisions when more options are available.. It would also significantly extend game time. It wouldn't double because mechs will die quicker, but it would be longer and would require larger maps. I'll try to dig up some official comments on this. I am pretty sure either Mitch or Jordan explained why they stuck with one lance at some point. I think it was in one of the Q&As.
I suspect that this is also one of the game design benefits of the initiative order system (it also has benefits such as giving and advantage to lighter mechs which are generally weaker). It makes each individual initiative segment have fewer decisions to make, and should thus be expected to streamline matches to help players get them done quicker.