I've been playing that way as well. It keeps me prepared if my favorite people end up dead in a mission I'm always able to play as whoever is available. I'm also frequently surprised at just how good some people are. Like I had no intention of using Machina that much, but I completely blew on the last mission and everyone died and he was all that was left. But his swords doing their drill attacks devastated the boss whenever I caught him. So thankfully I was left with someone powerful and not something like Deuce lol Just dancing around playing a flute that summons a fairy or something that does 50'ish damage randomly whenever it manages to catch an enemy..
Edit: There's that thing I abuse in random encounters that more enemies are nearby and it asks if you want to keep fighting. I usually get quite a few of those in a row and fight 4 or 5 groups before moving on. Gets you lots more stuff when you start fighting higher level enemies in those groups