You misunderstand a lot.  

Our dignity doesn't come from the sum of our physiological functions.

It doesn't come from how well our body is working.

Our dignity comes from our being children of God.

Too many Catholics are "buying into" the secular corruption of the meaning of our nature and the source of dignity.  

They've turned it egocentrically. 

Far greater "dignity" is seen when someone's body begins to no longer function well, and their family and loved ones - moved by the Holy Spirit - rush in to bring them love, memories, tender and perhaps very effortful care.

That's a far bigger and more beautiful form of "dignity" than what you're arguing for. 

The outpouring of the Holy Spirit is far more beautiful...then the Kevorkian contraption.