Throughout his history, Danny typically wears the mask during major battles.
In any case, I can understand that in a movie we'll see him either training, sparring, or having smaller conflicts without his mask on.
For that kinda stuff, ANY actor can be given a crash course in martial arts and then have a choreographed fight scene. Think of all the light saber battles in the new Star Wars movies. NONE of the main characters are experienced in sword fighting, yet the scenes came out great. Think of the Matrix and Bourne trilogies. Both had some amazing fight scenes even though the actors had a bare minimum knowledge of martial arts.
So mask off... use the regular actor. That's fine. Mask on... have the much crazier and faster fight scenes using a stuntman with martial arts experience.