Some information and tips on redshirts...
All players will "take" the redshirt - the only question is whether or not they will drop WE as a result.
If you inform a player during recruiting, and he signs with you, he will ALWAYS accept the move with no WE drop. The downside is during recruiting it's a bit of a negative. It can be overcome with more positive effort, but it means its hard to inform the player in a battle situation or if you don't have much cash left since it might cost you the player altogether and then it's pointless.
If you don't inform a player, he MAY still be okay with a redshirt with no WE drop. It's a chance you're taking; many players are still fine, but many are not.
If a player is unhappy with a redshirt decision, sometimes the WE drop is quite large (even dropping all the way to 1), sometimes its very small (only a few points). You won't know if he's unhappy at all unless you try, and you won't know how much (how many points lost) unless you try.