only a few option:
RAM must be 1.5 Gb unless (n9 spend 700Mb for UI only)
12MP obviously like N8
battery must be major than 1850mAh and if possible not Litio battery but Li-PO battery like iPhone
and the physical keyboard is the best thing
so u can write in all the screen cause QWERTY steal pixel
from UI and empty half the screen background

OS: MeeGo default obviously cause the swipe system open source is the best way for quick input interface
no WINDOWS if possible

i can spend also 800euro for this