I am pretty sure all of this is moot. When upgrading to POSv we had to reindex, the older wallets shouldn't be able to send coins to this chain even if they can connect, in theory it shouldn't accept any POW blocks because we are past the POW final block #.
I didn't need to reindex. I just started up the new wallet, once they added the difficulty algorithm. No bootstrap or anything, just a clean start.
Your theory is incorrect. The new wallets still consider the old wallets a valid node. As such, there are conflicting code rules on which blocks to accept. The old wallets say that POW blocks are correct and the new wallets say that POSv blocks are correct. Whoever controls a majority of whatever version is the winner now. From Cryptsy's standpoint, keeping the wallet offline is the right thing to do, just like CartmanSPC said. If Canna or Weed or any other MJ based coin wanted to cause havoc with the chain, they could, and Cryptsy would be setting themselves up for a big glaring hole. Just because the new version named a final POW block, it doesn't mean that it's written as law. Old versions, which are still accepted as valid nodes, say that things should have continued past that block.
Until the code specifically blocks out all old versions, the blockchain will still believe those versions are correct.
This is literally a simple number change that effects nothing else with POSv transition. It won't change staking, sending or receiving coins, or anything else. It will just block old wallet versions and plug the security hole. Patch it and move on.
-Fuse
You had to reindex when upgrading from 8.6 to 8.7.x, that is what I am talking about, you can't wreak havoc on a chain that the wallet doesn't understand. So long as the exchanges are running the latest wallet, which they have to be able to operate, they shouldn't have any risk of seeing POW blocks from the 8.6.x, seeing as we are now officially way past the # that is in 8.7.x for the transition.
If you really think that its possible, please do it in proof of concept and then reality, then show the devs what needs fixed so we can move forward.
Bittrex said they would bring theirs online when the upgrade error went away, it did. Now there is something else that is holding them back, I doubt its still the older versions on the chain.