impossible, santiago said quite some years ago, that the JVM can only excist due to the way it is build... while it is true that the 2203 was the baseline amp and used to sort out the design of each channel,Speaking of which chiliphil, I'm really surprised that some of the builders here on the MF haven't reverse engineered some of Marshall's newer more popular amp designs ONLY building them better than Marshall does. If this were to happen, you could be assured that Marshall would take note and very likely start offering custom hardwiring services for their various amp models.
the prototype JVM was pretty much built the same way as the production models
the vintage modern prototype was done in a more classic way, but that's a totally different circuit: