Hello! You are totally fine to app in a new character before the deadline, no problem. c:

As for Aradia's powers, you're right on the Time aspect and the summoning of the spirits being nerfed. As for hearing the dead, it's not technically nerfed, but there aren't any dead that can be heard as of now. However, that might change in the future as endgame goes along and things start changing, so~ In short, it's not nerfed so she's free to keep the power, but it won't be of any use as of right now if that makes sense!