^ Indeed none of the old KOF needed any voice over work. But this is the first time SNKP is doing a stand alone STORY Mode for a Canonical KOF series (MI kinda did that in a way). So to show that they are taking it seriously, having English Voice acting would be nice.
But like its been said several times, having the option to select which language to hear would make everybody happy. Besides, even if BB has some annoying voices, I really appreciate the detail they added. For example when certain characters fight each other, they will scream different things.
Which added a lot to the characters personality and rivalries. If BB didn't have English voices I wouldn't know what they were screaming at each other and maybe I wouldn't appreciate the characters more.
So I don't think that having English Voice option will hurt SNKP, heck, maybe it will help get more people into KOF even if they don't play it competitive. Of course, I say this assuming the game will feature a story mode ala BlazBlue. BlazBlue Arcade had a story mode too, but more off the lines of what you see in KOFXIII, just some small conversation boxes in some matches and an ending. Yet the console version came out and they did a full new story mode, which followed the Arcade version one, but it expanded. So I think SNKP might be trying to do something along those lines.