How's about this for a subbmission!, Vigo can be one of the supporting cast LOL, dont take notice at what i'm about to say.
Vigo is in a painting, the ghostbusters try to put him into a trap. It aint happening, Vigo is laughing evily saying how they can't destroy him, as his soul is trapped within the painting. So the ghostbusters, after getting Dana to clean the pic, take it home and hang in their offices.
Now we get Vigo plotting behind their backs, leading into GB2!, but at the same time he would help them, sort of like the ANTI-Hero of the new series. Eventually he would Betray them leading into the revamped story of that took place in GB2!. But until then he can be like the new slimer (since in this series slimer is evil) and he would be evil except hes trapped in their offices.
I know your gonan say how is this possible he has powers, he can use them. Well im sure Egon can think up something to surpress his powers, while hes hung on the wall. But he would be better than slimer because he would be unwilling to help the GB's unlike slimer, and he would stay evil, hows about that!
LOL i know im chatting jiberish, but its because ive just woken up and im having a hangover!