Does everything that is broadcast have to be incorporated into the block chain? I suggested a long time ago that the signatures not be part of the hash so that the signature data could be pruned out.
Signatures are already not part of the hash, that would make it impossible to sign a transaction. See the definition of SignatureHash in the code. (edit: sorry ByteCoin, I think you meant transaction hash not signature hash, right? I think the fact that the block chain is entirely self validating is pretty important though!).
Stefan - excellent suggestion. That's a neat way to do things. To sign for the control output then, the current bond owner would have to calculate owner privkey*bond record hash too to make it match the pubkey, is that right?