If we take Manziel it will make it almost impossible for Hoyer to be the starter... While many of us would understand the concept of sitting Manziel for a year - I can't say the same for Joe Blow casual fan.
That said... if we take a QB at #4 I think you need to start him regardless of who it is (Bortles, Manziel, Carr, etc) out of principle. Otherwise it is a waste of a pick on an immediate starter.