As a little aside, it has been scientifically proven the gene which causes red hair also causes faster skin aging and earlier wrinkles (independent of the greater sun damage redheads get due to having pale skin). So if the show does have a five-year run, it's likely the gap between Tilly's supposed age and Wiseman's real age will become more evident.
Someone should warn Karen Gillan about this. They'll need a TARDIS, of course.