Ryan Williamson of Dunfermline probably fits the bill for right back, for me, but as is usually the case, that's based purely on hype and not actually seeing him play, so he'd end up being shite.
Someone like Jack Grimmer probably fits the recent ideal of signing young Scots from the lower leagues, but again, never seen him play.
Marcus Fraser is out of contract this Summer too, but I've always had the idea he's a CB playing at full back.