I'm in touch with Katrice of Sonic HQ about an interview. It's still in the planning stages at the moment. I'll post details on the interview when it happens. I'm not sure what kinds of questions will be asked, but I'm sure it'll be fun regardless.
As far as ProSonic, I've added springs. The springs aren't perfect yet, but they're getting there. I also fixed the screen so it scrolls the exact same way it does in the original Sonic games. It really adds more of the original Sonic feel to the engine I think. One thing I haven't changed yet but plan to is the way the main counters work. Right now they're controlled by the Sonic object, but that's not the way they function in the original engine. So I will be making them automatic, even if player objects are non-existant. This would also fix a couple small bugs in my engine.