For me, it would have to be useable off line. Highlighting and notes would probably be useful but I think (apart from a reasonable search) that's it. The other thing is I'd like it reasonably compact.
I have dabbled on and (mostly) off with my own app using the KJV for my personal use (I did have a couple of apps on the Playstore for a while -
JfCupsPrint and a beta version version that can use the print services in KitKat,
JfCupsPrintService for sending print jobs to a CUPS server but I had too much in the way of personal problems to keep going with the development and won't be trying public development again) . The search which will handle references (eg lk 2, gen 1:3, etc) is about where I want it but I've yet to get round to highlighting and notes. The apk is
here if you want to have a look at it. Very primitive I know but with the highlighting and notes added, it would probably represent all I want.