I think you over estimate the % of the general phone buying pop that cares about the removable battery
Agree - I honestly don't know any S5 owner (4 in my own extended family, maybe a dozen at work) who has a spare battery. Unlike the S4, everyone finds the S5 battery life quite good and easily gets through a normal person's day. Once battery life got good enough, nearly everyone stopped caring.
There's always going to be the business/travel crowd who find value in it - unfortunately for them, Samsung seems to be focusing mostly on the consumer crowd.
mSD loss I do think is going to sting for a bunch of Samsung owners - as a surprising number have them, especially as 64GB card prices have cratered ($22 is pretty easy to find). It'll be mitigated to a large extent if 32GB really is the base storage like the Note 4, but Samsung and carriers MUST sell larger variants, at least the 64GB option. It can't be paper launches like in the past (though I do think a lot of that was on carriers).