Backdashing with up sounds kind of unintuitive to me, but I also think that it would be easier to use when I get accustomed. I hardly ever use backdash in most sidescrollers, and that's messed me up in more than one castlevania boss fight.
Down+Jump sounds more intuitive, but also harder to activate. Can you backdash out of attacks, like how Metal Gear Rising let you dodge-cancel? That would be totally awesome. It's always frustrating when I hit dodge and the character just stands there with their weapon out and lets the monsters smack them in the face.
I'm really finding these updates interesting, I hope you keep blogging about this new project.
You can crouch during an attack (into a crouching attack), jump during an attack, and dash from an attack.
It's more or less my intention for limitations to interfere with the player as little as possible.