A few things I would like to point out, first you mention Spy, The Heat and Bridesmaids as signs of Feig's capability. These to the best of my knowledge were all his own works, and ones he tailored to his go-to team of actresses. This is likewise true of the original Ghostbusters movie, that was written with specific actors in mind. I would have just as serious concerns about the quality of lets say a Bridesmaids remake starring Murray, Aykroyd, Ramis and Hudson. Especially if they each brought their own specific brand of humor to the film, rather then the humor the film calls for. My biggest complaint against the new Ghostbusters is that it is just not very funny. I have not laughed once at anything I have seen in the trailers. For a comedy film, that is a terrible sign. It looks and feels like a SNL sketch of Ghostbusters, rather then an actual Ghostbusters movie. I am considerably more tempted to laugh at the lowbrow hamfisted physical humor then with it. Add the overly cartoonish looking CGI ghosts, and that Feig seems to be mining the original movie pretty hard for ideas for his reboot leaves little for one to be excited about watching quite honestly.
Tavi