As far as I can see now, using difficulty as score for POW blocks, and let POS blocks inherit that score from the previous POW block is a good enough solution for the problem on hand. Whether one POS block following another POS block is explicitly ruled out or not, I think it should be ok either way.
The Novacoin solution of encouraging a hybrid chain only make sense because they have 1:1 POW:POS blocks ratio. YACoin is 10:1 with POW:POS. You'll need to check pretty deep into the past to encourage a 10:1 ratio. The score consistency problem I mentioned above could lurk in such schemes. Of course, we can also talk about the POW:POS ratio if people want to change it.
I absolutely agree with the ratio of 10:1 and when you think about it, it's more like 20:1 at least. We do not have many POS in YAC now at all, I do not understand why the sudden rush and madness to "fix" POS when there is hardly any POS at all. Has anyone looked at the blockchains that we are comparing YAC to, meaning PPC and NovaCoin, they are 90% POS or more.
Is there are alternate motive behind all this?