I don't see why folks wouldn't want oscar around. Hee could be a good tie to the past. With weaver, and they could take that one rumor that he is actually venkman kid. And we have sotryline of him growing up with the busters and always wanting to be one. That is a good background to go with him. Plus if they went around that idea he could also show/teach other new recuits the ins and out of gb tech and all that. Plus they could have him be the venkman type of the group. But on other hand I don't want the new team to just be direct rips of the original four archtype.
Oscar would be the perfect eyes-in, or maybe that's because he's around my age. Growing up with the Ghostbuster. Just a lot to work in for modern audiences. Jessie Eisenberg may also work there (Zombieland).
Could be seen archetypically, however - that's also avoiding the key notion behind those archetypes in the first film. The main gist is to bring in characters that although some may blend together, others it's more asking "how did these guys ever come together?" One is bookish, the other is eccentric, another is the strong man, and one is more of a late night talk show host personality. Within there - for any writer - there is a broad spectrum to play around in.
For example...
The bookish type could have come from a different country because he heard of increased paranormal entities in new york city. He could be more of a detective and sleuth as well.
The eccentric type could possibly be a computer nerd who knows how to re-wire everything in New York City and become the eye in the sky in a way. When he goes into the field he's stumbling all over himself, while he seems right at home behind a laptop which he brings with him.
The strong man could be a cop who got tangled up in a case that somehow relates to the paranormal and his superiors think he's off the deep-end in his obsession about it. He views joining a "ghost hunting squad" as a joke, but knows it'll open up some of the questions that he has and by the he end finds himself as part of the team amongst these wacky guys.
The TV talk show host personality, I'm unsure - but he could be one of the guys remaining or the boyfriend of a girl ghostbuster who gets pulled into it.
-- Basically look at the original --
You have one eccentric guy who is absolutely nuts about this stuff.
You have the bookish guy who is all into formulas and equations.
You have a scientist pulling outlandish experiments and not viewing any of it seriously.
And you have a guy who comes in out of nowhere, doesn't have the same know-how as the other guys and is more the straight man to their wackiness.
Basically -- Bruce Banner, Tony Stark, Steve Rogers, and Donald Blake.
Archetypes frankly work for a reason and within those archetypes trained writers have A LOT to play around with. Without going for extreme personality traits, all you'd get is straight-comedian actor working off of straight-comedian actor; part of why Ghostbusters works is the "how do these guys get along?" aspect of it. Completely different worlds and personalities almost, yet they all gel together perfectly. That's the key.
The problem with finding the 'strong man' - for me it would be Reynolds, Renner, and (a name that comes into my mind for whatever reason, might be how he portrayed kirk) Chris Pine - is that person needs to gel with the rest of the cast and have a knowledge of comedic timing. You look at who Winston is/was and he really shouldn't fit in with the others. Just like Steve Rogers really seems like the hardest to place in the Avengers. But, that character - whoever it is - is more the glue holding things together. The straight man is needed more for the wackiness to bounce off of and act as a barometer, the more straight-laced and serious (without too serious) that barometer is the more grounded things become.