Doc Fritz
I too wonder how Peck (should he show up, and I hope he does) and especially Janine will look. As they're basing the appearances off of GB1, I espect they'll look “sorta like Atherton and Potts” but not quite, just like the four Ghostbusters look “sorta like Murray, Aykroyd, Ramis, and Hudson”.
If Janine looked closer to the RGB Season One Janine, but with the slightly more conservative wardrobe from GB1, that would be perfect…
I Guaran-ice-tee you that Peck will show up. I was hinted by a VERY reliable source that he would. I hope that he'll have the EXACT same personality he had in the movie. He needs to be menacing, as Fritz would say, and not goofy, like he was in Big Trouble With Little Slimer. I wonder how he'll look, though. Maybe all they'd have to do, is slighly change is facial hair, and that way, they wouldn't have any legal trouble.
As for Janine, I hope she won't resemble/remind us of the new TMNT Cartoon's April O'Neil. That's just not Janine's style.
And remember Fritz, it's not sorta, it's “kinda”.