It really is a lot clearer than you are perhaps being led to believe.
You will find that the stock answer from the CAA is that FAA CPLs will not be validated unless you effectively do all of the work necessary to have a JAA CPL issued... If you are looking at the FAA CPL as some sort of short cut, you can forget it.
The route of buying an N reg and touting for business is also a non-starter. You would need to operate under an AOC (Air Operators Certificate) and your aircraft would therefore commonly need to registered in a JAA country.
Whilst N-reg aircraft can be incorporated on a temporary basis onto an AOC, you have to demonstrate why an equivalent G-Reg was not available, and the authorised incorporation will commonly not last for more than 6 months. Circumventing Flight Crew Licensing issues would not be seen as a good reason for putting an N-reg onto an AOC and the exemption would almost certainly not be granted.
To do what you want will require you to obtain a JAA CPL or ATPL (as appropriate), and there are currently few shortcuts.
2D