A) If you're going to make a steampunk reimagining of something, don't claim it's based on the original novel. Call it 'Musketeers' or something.
B) Make sure your actors can do some sort of accent if you have them in major roles. I'll accept the generic old-world accents (mostly British, not at all French) of the majority of the cast, but the kid playing D'Artagnan sounds like he just walked out of Brooklyn.
C) Ending on a positive note: At least the effects in this trailer have improved?