In past titles, was it possible to fight the harder monsters first and then the low-tier ones? Or is it going to be possible in this one? That could be interesting. Although I don't know if I'm missing the point in something that makes crucial to fight monsters in a more sequential order. The basic premise is very tempting, though. Sounds like an ideal time-sinker.
You can do that, but whether you should depends on how they structure the quests and items drops in this game. Playing World recently, the way it works is you can freely hunt any monster in a new area you've unlocked, but you won't actually unlocks quests to hunt harder monsters until you've progressed enough in the main storyline.
Quests are very important because you get a lot of bonus materials for hunting monster through quests, rather than through free expedition. But you do have that freedom regardless if you're more interested in the challenge.