For a US based DL flyer, I fail to see how this even comes close to working.
One would be unable to obtain any status, and this really sucks. Try picking seats on DL as a kettle. Welcome to 44D.
And on RDM accrual, you are now comparing miles based non-status accrual with status adjusted $ based accrual. For the average FF DL flyer, that seriously changes the numbers.
For this few who use both airlines, I could see the point. But they probably already know how to run the numbers.