I loved the design of the Cadillac DeVille since it came out. It is a large sedan and looks like a Cadillac, not some scaled down "whatever" style that they've come out with since. It provides elegance and comfort for the 50+ crowd - we are the "market" not the kids who can't afford a Caddy anyway. You are losing your market and don't know why? This car caresses the owner and gives max flash for your cash. Isn't that the point? Just bring back fins and no-draft windows and we'll all be happy. So sorry you don't care anymore, but this one was a WINNER!
The self-dimming interior mirror and MASSIVE trunk.
Add more lateral stability to seats and a higher roof line. The interior mirror creates a blind spot in a few situations.