Um….
First of all, a 7083 people production might be a little hard to control. Second of all, There would be too many petty arguements over what happens and such. Third of all, it wouldnt have the magic that danny and the originals (including some of the production team)had. They had a chemistry to make hit movies plus years of experience. Another reason is that it wouldnt be released, inspire a new cartoon, action figures, comics and etc. It would lose the feeling of it coming out(I hope that makes sense). Its a good gesture and all but I dont think it would work. It would be better if we left it to the proffessionals. Unless its a fan film youre talking about, then you could just forget about this post.
And I dont think Ivan Reitman stopped the would-be production of the third film.