I think Eliezer is saying cryonics is a positive good

I don't think so; when people say "shouldn't you argue that people give the money to SIAI", he says "why does this come out of our saving the world budget, and not your curry budget?"

I think this is a very weak point and the far future will probably be able to make whatever kinds of minds they like, but we could have scanning/WBE long before we know enough about minds to diversify them.