Sales would be far too low to justify investment in them, especially the vehicles you mentioned, just to support a brand name.As you all know, Mercury was designed to be a bridge between Ford and Lincoln. The Ford brand instead starting overlapping Lincoln and there was no gap. My 2006 Milan has more style than the 2006 Fusion. That is why I bought it. However, I do not think Ford could continue to produce clones of each other. Fusion, Milan, Zephyr (MKZ) or Escape, Mariner, Mazda Tribute. Instead, they should have made Mercury a niche brand.
How about a 2 door coupe with convertible option or take Flex out of Ford and put into Mercury, with some re-designs, etc, etc. I am sure this has all been discussed before, but this is my opinion.