Just my 2 cents:
If eInk screen could be made to behave the same way as LCD - it would've been made already saving you a lot of time
Just think about it - do you really believe that people who modified Android for eInk platform are that bad?
Doing what you actually want properly requires big Android redesign and reimplementation and even than result may not satisfy you anyway. eInk is different - no matter how hard you will try to switch controller modes. Looking for magical value is pointless. Today if applications you are using are not designed for eInk - result would not be good.
Doing decent work on application level however is entirely possible - and that is what WebBrowser demonstrates and platform supports.
From what I could see By default driver/controller are in AUTO mode - drawing using fast and dirty modes do not require switching. WebBrowser controllably switches in FAST ANIMATION mode (A2) during zoom and scroll and full refresh (UpdateMode = 34) is used to switch controller back and requires delayed full refresh (800 ms according to original WebView code). Otherwise controller stays in A2 mode (rather than AUTO - default mode) and you would immediately see this on your screen. If you want to avoid full refresh - do not use A2 mode and draw using dirty modes (DU,GC4,GC16) instead - as I said they are compatible with AUTO. Driver and controller support drawing of up to 16 regions on the screen - each with it's own mode - simultaneously. When you go over some complexity threshold - full refresh will happen anyway as controller cannot handle it.
This information is all over Web - on FreeScale web site, Nook forums and in Sony code...