I've got a "workaround" for this issue. Still, it requires a hard-fork.
It's quite simple, just disallow two consecutive PoS blocks and lower PoS trust to match PoW (1).
There's no way PoS-only miner can orphan a single block.
Matching PoS and POW trust has enourmous consequences so we have to be very carefull here.
The biggest problem is that it'd be possible for PoW-miners to turn YAC into PoW-only!
Once we are there we couldn't get back without a hardfork and it's unlikely we could possibly agree on such by then. PoW is far more important than just distributing initial coins.
and unable to secure the network later on since f.e. it can be centralized.(I've written someting about that on yacointalk, that's also why YAC is special)
I belive the current problem of one PoS-block overwriting more than 6blocks is far less than the problems we would get when we have no more or just a bit PoS. PoS as whole has to be much stronger than PoW so that all miners could
n't agree on "just ophraning all PoS" to make more profit. A PoW-block will always have more new coins than the average PoS block so most PoS would disapear and the rest 'd be centralized.
PoS mining is truly decentralized so we should try to keep it as important as possible.
I can't think of a technical way to prevent doublespends AND miners from fighting PoS.
What we could do is increase PoW-rewards for miners that mine on top of a PoS block.
It must be either chaintrust PoS>>>PoW or new coins generated in ...-PoW-PoW-
PoS-PoW >...-PoW-PoW-
PoW-PoW. We all know that PoS>PoW is problematic so we should go with the 2nd.
I'm glad you've got something in mind, I've spent a couple hours trying to find out what the fix novacoin implemented was, even digging through the code, but I can't isolate a single POS fix - there have been quite a few tweaks to POS in Novacoin. I can see that they currently have adjacent POS blocks, so what did they do to address this issue?
AFAIK Novacoin "fixed" this by having a centralized checkpointing system in-place. Essentially one person controlling the whole network (deciding on the valid chain), which defeats the decentralized nature of cryptocoins.
A centralized checkpoint for the next few months would be far better than loosing or having less PoS in the future than we have now.
The only issue is deciding on the blockchain fork date. It should be fairly soon, but not too soon as we should give a majority of the network time to upgrade. How about 1 month?
I think that's reasonable.
EDIT: Sorry smtg wrong
EDIT2: Added stuff in RED.