So it's mid to low end phones for you from now on? Because those are the only things left with removable batteries, and there's no sign that will change (the opposite if anything, I'm afraid).
As for the FP scanner, I can see pros and cons to all locations tried so far (front, back and side), so am pretty agnostic on this. It wouldn't take me long to adapt to any of them. I don't think the S8's off-centre placement is good, but even that I can handle without any difficulty (right-handed - it's more awkward in the left). It's worse for me on the S8+, and so probably also on the Note 8, but that's really down to the size of the phone. So I guess my conclusion is that I'd prefer it centred, but for a phone of the size I might buy it's not such a big deal.