I think Bill would do it if they had a script in place that pleased him...to me that seems to be the problem with any of these attempts, there isn't a script that is of interest to him.
Since you're apparently on a first-name basis with him, maybe you can ask.
No, Murray's reluctance (and now, refusal) is due to two factors: One, he had a terrible time on Ghostbusters II
and it really soured him on the franchise. Two, he and Ramis still have never really mended their fences since the complete and utter falling out that came about because of Groundhog Day
. It's not a Cold War like it was until about 2004 or 2005, but the two are still not anywhere near being on the best of terms. Murray's a very sensitive guy, and he was very hurt by Aykroyd and Reitman on Ghostbusters II
, and he felt incredibly
hurt by Ramis on Groundhog Day
. He very clearly doesn't have much interest in resurrecting a franchise he isn't terribly fond of in the first place, especially when there's no real creative reason to do so.
I'm fuzzy on the whole good/bad thing... what happened in Groundhog Day that split them apart?
Murray felt his character, and the story, should be played completely seriously, as though it were a drama, while Ramis said, "Come on, this is a comedy." There were several large blow-ups between the two on the set, and it culminated in Murray, after his last scene was completed, going over to Ramis and saying, essentially, "I have nothing more to say to you." Ramis reached out several times throughout the '90s and the early parts of the aughts, but Murray didn't return any calls from Ramis until something like 2005 (I believe that was the year; I need to check my interview notes); they're on speaking terms nowadays, but Murray is still pretty hurt. I'm sure that part of it is him being childish, but, really, he's earned it.