I would love this too. I think it's called being a consultant
Really though, great idea. I've thought about doing this too, but I'm pretty sure none of my employers would agree. One of the frustrating things in product development is that we're usually not allowed to discuss our problems nor their solutions because they are confidential to our employers. However, I'm pretty sure that whatever "secrets" you would find out would be more than compensated by the knowledge my org. would gain from you.
To conclude, how do we make this happen?