The other big problem that doesn't seem to have been covered with playing Nunes at RB is this: what if Nunes, our OK-ish but not great RB is injured and our next game is against a top side, a game which we must win?
Then we're downgrading from an OK-ish to, a "maybe OK, I least I hope so" RB. This is far from ideal.
We need a top class, first-choice, starting RB - and Nunes can provide backup.
Yes it's possible that our first choice RB is injured and can't play against a top side - but we'll have Nunes as backup, at least most of the time.
The alternative - Nunes as first choice RB - and some patchwork fill-in as backup - is obviously sub-optimal.