It's an interesting concept, making your own photos for a game, but the risk is also much higher.
When you're using 3D models, they don't need to be paid, they're available 24/7, and you can slot them straight into whatever crazy scenario you envision. With a real-life model, there's limits to what they'd be willing to do, and there's always the risk that real life will get in the way, and they won't be able to commit to the project after a point. I mean, it happens with devs themselves on a regular basis, and they have more invested in these projects, so it's very likely that it could happen to a model. And replacing models after they've been around for a while is a guaranteed mood-killer.
Sorry about the pessimism, hope it goes well, but it seems like quite the challenge.