On Wed, Sep 23, 2015 at 3:43 PM, Gavin Andresen via bitcoin-dev
<bitcoin-dev@lists.linuxfoundation.org> wrote:
[...]
> A miner could try to avoid validation work by just taking a weak block
> announced by somebody else, replacing the coinbase and re-computing the
> merkle root, and then mining. They will be at a slight disadvantage to fully

Take care, here-- if a scheme is used where e.g. the full solution had
to be exactly identical to a prior weak block then the result would be
making mining not progress free because bigger miners would have
disproportionately more access to the weak/strong one/two punch. I
think what you're thinking here is okay, but it wasn't clear to me if
you'd caught that particular potential issue.

Avoiding this is why I've always previously described this idea as
merged mined block DAG (with blocks of arbitrary strength) which are
always efficiently deferentially coded against prior state. A new
solution (regardless of who creates it) can still be efficiently
transmitted even if it differs in arbitrary ways (though the
efficiency is less the more different it is).

I'm unsure of what approach to take for incentive compatibility
analysis. In the worst case this approach class has no better delays
(and higher bandwidth); but it doesn't seem to me to give rise to any
immediate incrementally strategic behavior (or at least none worse
than you'd get from just privately using the same scheme).