I'd add more than 2 teams to be honest, and would better randomize interleague play and get rid of forced Mets-Yanks every year. You play a random small subset of the other league, 6 teams maybe, varies, randomly. Maybe a weight for subway series stuff, or by request of owners or something, so they happen more often, but not every year. Travel isn't as bad as it was, but we're learning more and more how much lack of sleep, and weird schedules can mess with you, performance wise, so it's still important. travel time from Seattle park to Seattle airport to JFK to your home is still a long travel day. I'd add at least 1 team near Seattle, but maybe 3. Vancouver, Portland, etc. And on the same travel vein, since Mexico City gets mentioned a lot, 2 teams, maybe more, there. Same division so they get a lot of lesser travel days to make up for how far they have to travel otherwise.