Toothless, seems to me you will want to run 1080p-4K-1080p mixed resolution LLL (AMD specific, as Haldi implied), along with Windows 10 scaling to line up image. It sounds like an excellent setup, with high detail center & light sides. I hope you succeed.
I am thinking in the same direction (but for PLP). If it works well, it will create incredible flexibility for multi-monitor. I don't know yet how well Win10 will scale individual monitors (I'm still on win8.1). There is a pretty high chance this Win10 feature will not be great for MM fullscreen gaming (might not look good, or be useless, or broken in a common scenario). But it may look good enough, or even great.
Related Win10 scaling questions were posted here (no-one answered):
http://www.wsgf.org/forums/viewtopic.php?f=68&t=30145We may have to test it ourselves. I'll get to it in a month or two, hopefully someone else will answer first.