tech support for the newer generation (that theyve had to subsequently hire)
That's exactly how I see it, you'd have the old gang working part time at GB HQ and also doing they're own thing, while a new team go out doing the ghostbusting work. Egon and Ray would spend all their time back at HQ being geeks while peter and winston take part time work elsewhere. the new gang get into big trouble, then the old team have to step in to help out. It could work out really well if they cast it right.
Oh, and Slimer needs to be in it too, cause he could give some good comic value.