LOL. You should email Tim Cook. Clearly, you've thought this out. WAY more than they have.
Regardless TouchID is a superior method. It's fast (especially on the 7/7 plus and MacBook Pro) and convenient. On the iPhone 6 it was too sensitive to oil and sweat. It would give me a hard time working indoors. With the 7 there are no longer any problems. It's really a shame they can't incorporate it under the glass. That would be extremely impressive. I hope they don't give up on it. Going from touchID to "faceID" to go back to touchID under the screen would be ridiculous.