I guess i'll chime in here, since I want to make a simpit too.
Although I have a slightly different mindset. I have yet to find a good resource for making a cockpit to your liking (correct me if I'm wrong here). And generating the input has always linked to modding a consumer grade joystick or the outdated Mjoy.
So what I would like to do is design an interface for "your" cockpit to connect to "any" flight sim using new and improved technology!. Someone already talked about an Arduino, which is my plan exactly (If you don't know what it is, and you are mildly interested in electronics, its the best $30 I've ever spent). The new Arduino can emulate virtually any HID device [Keyboard, Mouse, Joystick, etc.] along with inter-process communication [Arduino <-> Orbiter]. The interface is also modular, so you can fly Orbiter one day, and the next fly MFS (with appropriate changes, but same interface).
I have some scribbled down notes. So far its a 5 phase project, with phase I & II being the core of the cockpit and being applicable to any sim (basically just keyboard and joystick emulation). III & IV are program and / or ship specific (Orbiter; Ravenstar or DG, DCS Black Shark, X Plane, ...). Then V is just extra aesthetics. At the end, I would release the code, basic plans and how-to's. At that point, it just becomes a question of hardware.
That's the game plan. I still need to refine how I want to approach this, and I still need to dive into the orbiter API and get my hands dirty. But it seems feasible (but I may be way in over my head).