I know that it's going to have to all be on a single save file, but because of this I would rather play through the angel route on a separate save and then play it on the main save to get the third route. This way I can more enjoy the adventure with an appropriately leveled team. Because God knows that playing a second time, you're just going to steamroll through everything.If 3rd route does indeed require the 2 main routes to be completed (and therefore NG+), it would make sense that it would be part of the post-release updates.
Although, it's possible that the 3rd path was just meant to be a secret? (kinda copium, I know...)
Also, I want to see if there's any differences in the plot if you decide to switch routes during the great choice, it feels like an obvious thing to do even if it would only be minor changes. Kinda like the kill Alice ending.