I'd rather it be a reboot/passing of torch. With the (remaining) old Ghostbusters training a younger group and sending them on their own way. Sort of an "eXtreme Ghostbusters" sort of thing.
Murray not being involved is fine, whatever. He can be funny but he's a huge asshat prima donna
anyway and really I think he was one of the bigger "weights" in the second movie.
I'd also like to see Ghostbusters take a more harder action/adventure sort of position than a comedy. Taking the subject matter a touch
more seriously, again, like say the "Real Ghostbusters" did in it's first couple of seasons. The first movie more-or-less had this adventure-comedy element to it. The second movie very much took more of lighter elements of the cartoon and had it overshadow the serious/realistic aspects of both the cartoon and movies.