My pick - Prentice. He's got a bit of class, at least, and is not a total moron. Heck - maybe even a former premier like Gary Filmon, or something along those lines.
Although Harper "united" the right - he's morphed it into something unattractive to the swing voter. Part of the reason the bench is so thin for replacement for him.
I wasn't a huge Reformer fan - but I did like the idea of more grassroots control, and more power to the MPs and away for them PMO. Harper has all but destroyed those concepts in his party - in which HIS MPs are not allowed to talk, or only nod and smiled when directed to.
One conservative I'd consider voting for if he were in my riding would be Scott reid.