Its buggy, but it's not really a possession, it was more of a forceful consent using their blood to send Anti(whole) and Vi's consciousness (wouldn't work if she was awake).
Dante can move just fine. It will be a lot later when Trace can use possession similar to the heartless itself from the games.
Hey just to give you a bit of a rundown on my post, highlight the black after you've read it lol.
the idea comes from DDD when Riku jumps into Sora's head to fight nightmare ventus, but done using my hyrbid's ability of possession. Trace is pretty much trying to help Cal tame Dante, but it requires Dante to be active. Essentially what this means is your heartless is actually going to be put into a position of making an active decision to protect you, from my heartless who's trying to eat her lol.
Alsoooo the kiss was just for dramatic effect, once you took in Trace's blood the time limit to possess Calpurnia/Send Anti into her heart started. I just thought it was devious to do
Ari: Yeah I like them for the most part, the eldest out of us is the leader and the strongest. I just get frustrated at times because it seems like I’m only ever seen as part of the whole and not as myself. Um, sorry... I didn’t mean for that to come out.