The more ambidextrous the better! I am speaking from experience here because my right leg is still way stronger (like, visibly) than my left leg just from my early years of scooters. My left leg has never caught up.
For the mongo thing, it really is not a big deal to switch it up. Think about it as an instant boost to your style. Sure, if you need to use your front foot to get speed for that twenty stair no one is going to trip out, but if you are doing a lot of lines it will become painful to watch. It is just like learning tricks the opposite way, it takes time and feels strange at first but it is worth it.