It are also makes bosses with multiple phases where they change their attacks/weaknesses or other tactics where they change how they fight mid battle easier to deal with.
Mostly unrelated to traits, but on the subject of switching party members in combat I played a game ages ago called Unlimited SaGa that had an interesting way of doing it: Every round of combat you could choose 5 attacks from any party members and they would just kinda jump in combat for that round if they were doing something and jump out of combat if they weren't. Only exception was if they were hurt or unable to move they wouldn't be able to jump out and their slot would be occupied until another party member rescued them. Just thought I would share that, though I don't expect anyone to try and replicate it. I thought it was a really interesting style of combat, but not sure if it can be replicated well in MV anyway or if it's even a good idea to try.