Interesting proposal with some nice properties, although I mostly agree with monsterer that the long-range attack problem isn't fully solved. I'll look into the updated paper this week to comment on it.

Only a little observation (and that's why I comment here in the old thread): The attack monsterer described (old majority stakeholder(s) taking over the chain with a double spend) is essentially the same attack than a profitable 50+% PoS attack. In a profitable 50+% attack, you will wait for a few blocks selling your stake first (most likely in an altcoin exchange as they confirm the "reception" of the coins relatively fast) and only then try to "take over" the new chain with a prepared attack chain. Otherwise, very likely your stake would decrease in value. So, also in this attack, in the moment you take over, you don't own stake anymore (or at least, you aren't forced to own any stake).

The difference between "long-range attack" and "profitable 50+% attack" be the time between the actual double spend and the "takeover" (when the attack chain replaces the "honest" chain) but the attack mechanism is the same. But monsterer is absolutely right and this is the reason why PoS protocols are to be considered - until this is solved - weaker than PoW protocols. I consider this attack unpractical in a chain with many stakeholders and reorg limits or "rolling checkpoints", and it's likely to be very expensive, but it may be considerably cheaper than a PoW 50+% attack.