Fair enough. I don't see how it would be much more of a hassle than not redshirting, and you'd get the benefit of the extra year for late bloomers. O-lineman especially could use the extra year of physical development in my mind.
The benefit is that you have all 85 scholarship players available. There is no worry of pulling a shirt late in the year or whatever. If a player hasn't contributed by year 4, the chances of him being a contributor year 5 is slim. If you recruit well, you should have recruited over that player by then. If you are depending on 5th year players with limited experience you have bigger issues than whether or not to redshirt players.