Ozil would be fine as a backup mid for 20 mill. Having him as our dead wood rotation player instead of Gomes/Arda/etc. is actually an upgrade. Though he really could go the Arda route with his innate laziness.
The problem is, this is probably the board's idea of a "midfield solution" and Ozil becomes yet another mediocre player amongst our midfield fighting for a starting spot while no real world class mid is ever brought in. Wouldn't be surprised if he came and then they try/fail on Coutinho but point back to Ozil as our "midfield fix" and the cycle continues.
In the right context, this could be a good deal. The chances of that happening though are so slim that Ozil will likely just become another addition to our woes.