Nice work!
That's almost exactly the direction I'm heading with the cross-platform testing framework I've been working on, although I was planning on storing blocks in JSON format and was planning on using Python's Twisted/Trial framework to feed the different chains to the implementations to see if they accept or reject them.
I got sidetracked by the 0.5 release and then sidetracked again because I couldn't resist experimenting with the "OP_EVAL" idea and multisignature bitcoin addresses...