What i ask myself, when the old nodes only see empty blocks, aren't the transactions needed to calculate if the block hash is correct? If the transactions are not seeable then how can the hash be calculated as valid? As far as i remember, changing the transactions of a block will give you another seed part that is used as base to find the block hash.
You write that segwit miner still would need nearly half of the network to do this fork but wouldn't it be sufficient when 10% segwit nodes find a block, let's say a minute before the 90% non segwit nodes, then they propagate it through matt's network? or through other fast connections to all the big miners and these miners can instantly confirm the block because nothing big to be calculated. They would accept the block and that would be it.
Though even then, the old nodes would still think the bitcoins, that were moved in the segwit block, are at the old addresses, wouldn't that mean a fork of some kind has happened because a big part of the network has other details about the status of the bitcoins?
I'm surely not so much into the tech so i might be fully wrong.
