Oh that's good news! I'm excited about this
I'm a German speaker myself, but the dictionary is for my Japanese friends who are learning German. The kindle paperwhite has the best on-the-fly translation dictionary function from what I've tested, so the paperwhite dictionary would be my main aspiration. iOS would also be excellent - and for that matter even a MacOS Dictionary that works with the built-in OS dictionary look-up system. (I'll promote your apps in my facebook!)
Regarding the complexity and layout of the dictionary, from my experience reading a foreign language on my kindle, I'd recommend it to be compact and more of a translation dictionary. I find1 that I usually just glance at the translation and continue reading, as for an advanced dictionary look-up they all have their Casios ^^
You're a savior!!