[amscanne]

I think my points are valid.

What I mean by initial blockchain is that the initial bitcoin nodes you are talking to indeed represent the legitimate bitcoin network, and not a malicious network with an independent blockchain (valid and verifiable, but obviously would be shorter).

I think it would be straight-forward for ISPs to perform DPI and magically redirect and rewrite packets in order to have you on their bitcoin network with their blockchain. And you wouldn't be able to know if you had never seen the real blockchain.

If this is not possible, I'd be very interested to hear why not :)

A long time ago, I worked at a company that got its start doing exactly this for p2p networks in the early 2000's (and saving ISPs a ton of precious bandwidth).