I suppose it could be good. Your character would be a Jew who's family was killed by the naughty Nazis, then you are taken in by an assassin group who train you as you grow up to become an assassin. That sounds alot like Assassins Creed 2 but what else is there?
Just keep the feel and climbing of Assassins Creed, keep the hidden blade, let us run around Berlin and use stealth to kill guards on rooftops and avoid spotlights, and let us blend in with the crowds to avoid patrols and such. Let us take disguises of German soldiers and maybe give us the option to seduce the guards or assassination targets. Chase sequences and the consequences for being caught would be much more intense when you're being sniped and shot at.
I just hope we wouldn't get to use guns, there'd have to be a good reason for not using them too, or just give us a silenced pistol with a small amount of bullets in each mission, that is used like the throwing knifes in Assassins Creed 1.
Sounds pretty good huh?