1) So I fire up 2000 nodes, all selecting 200MB as cap.
2) I make the miners belive this is the prefered block size.
Why do you believe that miners are really that stupid?
My point is that it opens up to sybil attack. My suggestion is obviously a quick and dirty model.
EDIT: How would miners actually know what the "real" consensus is? Ask around on the forum? What if I set the blocksize to 14MB. That would still knock off plenty of nodes.