Yeah, I think rushing an all brett fermentation could shoot you in the foot. Especially if the yeast are not done fermenting and you are left with too high of an FG. On the other hand, I have noticed that brett seems to clean up after itself as it goes along almost reducing the time necessary to allow for conditioning like most sacch. strains benefit from.
As stated above, my only true concern with speeding it up would be the overly high FG leaving a sweet finish for that style. I would bump the temps to the mid 70's and swirl the fermenter a couple times a day to keep them yeasties workin.