No.
They are playing in right positions for this system. Fellaini will stop most balls from the mid so that the CBs don't have to come up to deal with first time balls all the time which can make them out of positions. Fellaini has been excellent at it. Blind can mop whatever he and bailly spill in case with his superb reading of the game.
But, fellaini can't pass as good as blind. So blind does that passing from the deep. The 3 of them, 2 Cbs and him fit together. Playing smalling instead of blind and putting blind ahead of him would upset the whole balance with how we like to defend as a unit and distribution from the deep.
Very simple and effective system. People like to move players around coz they like a player to be in first IX even when the system is working.