Speaking from what I like: Bonus action all the damn way.

Speaking from a balance perspective: I have no idea if that's healthy. Maybe upgrade it to bonus action at a certain level or is that making it too complicated?

On the feat I still say wisdom. Not because it's what is closer to dragons but because it feels like the dragonborn is unlocking these aspects from inward. These all feel more active than charisma as a stat feels. Charisma feels more likely to connect with the dragonfear power in 4e.