Better the old guys as cameos than nothing I guess.
One very difficult thing ( which you already partially pointed out above ) would be to make a film with the typical “Ghostbusters Style”. You know what I mean? Those movies have a feeling on them which no other movies nowadays have.
Well, I guess I can´t put it in words properly. I hope you know what I mean.
Btw : Sorry for spelling and grammar mistakes, I´m German after all.