The possibility of keeping Alex Smith.

[The Franchise]

So you've got your scenario above or the following:

Trade Smith for draft capital and gain $17 million in cap space.
DJ and Hali retire freeing up cap space.
You wouldn't have to get rid of Bailey....and you would have enough space to re-sign Logan. That would keep the entire defensive line intact going into the next season.
You'd have the money to re-sign Mitchell if he's proven worthy of one.