Originally a long-running Broadway play, 'Harvey' is best known for the classic film starring James Stewart. In fact, that film is so near perfect, one wonders why Spielberg is wasting his -- and our -- time making a new one. There isn't a SINGLE thing he could do that would make his film better than the original. And if you can't make it better, do NOT try.
Forget this one, Steven. There are thousands and thousands of original scripts and exceptional books out there. Find them and make them. Forget the remakes -- especially this one.
It's an even worse idea than the fact that you're now developing an Indiana Jones 5(!!).