Okay. Being neither a lawyer nor a hard core developer I can't really argue with your conclusions, though from my limited understanding there are ways to honor the GPL while keeping the sources of your "value added" parts closed. (Diffs and hashes and 3rd party audits, etc. After all, if you can prove that the GPL sources you DO provide recompile back to the corresponding pieces of GPL binary you ship, that should be enough.)
I mean, lots of companies do it! I come across them all the time, and some of them even appear to make money. Fonality / Trixbox is one that I was just looking at a few days ago. They have a "Free" version and several paid premium versions, but ALL of them see to be GPL licensed.
They do have a more closed, hosted companion service.
No, I don't have any idea how they keep from getting ripped off when their paid customers decide to redistribute. Frankly, if it takes going to the evil lengths that Sveasoft has gone to (essentially waging a war against its own customers) then I'd rather people just take your approach and stay closed.
In a realm outside causality and function