I'm not really a fan of the many variations of the premise that pops up now and again "The daughter of one of the Ghostbusters discovers the equipment." I really wanted a sequel, too... back in the 90's. But it's just been too long for me. All of these stories kinda remind me of Kingdom of the Crystal Skull. I'm pretty sure the studio thought we would want to follow the adventures of Mutt after the film. But the majority was like... umm... no. We're here for Indiana Jones (or Crystal Skull sucks!). If we actually got Murray, Aykroyd, and Hudson back we wouldn't want them to hang up the flightsuits and they'd overshadow the new team, even if they are really old and out of shape.
Feig's protecting those original films and distancing his from theirs to make something new. And I know many of us read a bullet outline of the film and there are similarities, but really they're reduced to they make packs, find a home base, get a car, and slowly form a ghost busting squad... the same thing any movie like this would need forming an origin story. It's the story in between, the one we don't know that counts and will differentiate us from the original team.
Yeah, I'm pretty sure Sony and others conceived of many stories connecting the films. They're daughters, they're students, they're whatever... but, honestly, since so many of us have come up with the same idea like, "no duh, they should have done this," it doesn't sound any more original than doing an alternative universe. Only an alternative universe can do their own thing, and I hope they do.