........
I do not think the first two statements are true and I'm pretty sure - as I pointed out - that the last statement holds true for POS aswell.
Temporarily offline peers and new peers will be able to tell which chain is the better chain only with blockchain data in POS. I'm not sure how exactly those scores are calculated (and it probably varies between implementations) but i'm positive that it's of absolutely no relevance from which peer it comes from. If a peer were to fetch "bad" data then it wouldn't have to verify with some "famous" node. Any none evil node would be enough.
If you're talking about the initial sync mostly happening from well known peers...well...you're gonna need well known peers in any p2p network or how are you planning on letting peers find each other ?
Guess I have to say things are not that optimistic in PoS. I might give you an example of attacking an ill formed PoS design for illustration purpose in the near future.
One question you might think right now is: Why PeerCoin needs to broadcast checkpoint regularly? Why NXT have that kind of restriction while Bitcoin does not?