One cock ring to rule them all?
Don't make the movie.
But, if you must, probably a reboot or a clean cut handing of the franchise over to some new faces is the next best idea. But if you've gotta use the old guys and Bill won't play ball...
Get Jack Nicholson. Who cares if he's old, he'd be great. He looks as good as those other bastards anyway.
Best idea ever (as someone mentioned below) - Bruce Campbell and (I would like to add) in the role of all the Ghostbusters!
To me, all they really have to have is a moon base and a Kubrickesque approach to their direction and story-telling in order to make it truly connected to the original show in any meaningful way, besides just the name. Paying homage to the original show through updated designs and character names is a no-brainer. Even a more modern approach to a Protean shape-shifting character could be cool.
What I'd like to see is a show that takes a realistic look at futurism and fringe science (and where the fringes might be nearly 100 years from now) crossed with enough character development and drama to keep it interesting. I think Space: 2099 could be a good platform for that.
I'm intrigued.