[Elagost]

We've been looking for a second ereader as my wife has been eying my Kindle Voyage, and I'd like to get something about the same size. I looked at the Kobo H20 2, and that looks almost convincing too, but seems maybe a bit too big. I like how my Voyage can live in my back pocket.
I'm very into having a more 'open' ereader that can deal with more formats - been using Calibre for over 5 years and it's got its fair share of quirks.

Priorities, in order of importance:
Small size
light weight, easy to hold (the Voyage is an ergonomic travesty)
front-light screen
high resolution screen

Nice to haves, in order of importance:
blue-light filter (a la Kobo)
page turn buttons
flush screen (non-recessed, like the new paperwhite and the Voyage)
waterproof

I'm almost convinced to get the new paperwhite, because it's basically what I'm looking for, but having a blue-light filter would be great too. The Kobo H20 2 seems maybe too big. Ideally what I want is a waterproof Voyage with a blue-light filter.

Any thoughts? Thanks for the help in advance!