I just had a thought, might be an interesting suggestion. I was thinking that the Hadouken can become pretty useless to someone who hasn't perfected the game. Especially because of the rule to need full health, be on the ground, and input the command. But that could be changed. It would require changing the color of the sprite and changing the code a bit, but you could have two versions of it in the game. The concept is to use the Smash Bros. method.
The original, full powered version of the move could remain exactly the same.
But, you could also have a version of it that is basically just holding forward and hitting the special attack button. This version could do 20%-25% of the damage that the full powered version does. That way, when you earn the move, you can still use it without needing full health, but it does nowhere near as much damage as the command input version. I would also suggest recoloring the sprite for this one to being red, like how the color would change back on old consoles if you spammed the hadouken in Street Fighter II. Though this step isn't exactly necessary, would basically just show players which one they are using. I mean, this whole thing isn't necessary, but I still figured it was a decent suggestion.