You look at this the wrong way. You are asking wether or not this offends God, wether it is acceptable.
Try this:
Could a tatoo bring glory or praise to God? Why yes it most certainly can. You are all right in saying that it's permanent and if you don't like what you got you're screwed. So what is something that you will never be ashamed that you got permanently embosed on your body? Well lets think about this... what is something that is permanent that you keep on the inside? Your faith, your salvation, your love for the Lord Jesus Christ. Now, couldn't a tatoo be an outward symbol to put on display of the inward faith you have? Yes.
In fact, i believe that religious tatoos are a very effective way to make a standout case for the Lord.
When people see that you have John 3:16 or a cross permanently colored into your skin, it makes a very strong statement. It shows that you believe and are dedicated to believe and that you have such faith that you don't worry about the permenance of a tatoo.
So, if you get a tatoo, let it be for the glory of Lord and let it be an outward testimony to the inward ways that God has touched your heart.
Prox