I think dumping Merc is a smart move, and yet I'll kinda miss it.
Take Moon Unit for example. The differences between it and the Taurus, styling-wise, are so small as to make the whole effort a colossal waste of time and money. Same thing with the Tempo/Topaz- the unlit "light bar" across the front of the Spaz being the only real difference
So back in the day they surely didn't put enough effort into differentiating the Mercs from the Fords.
But recently, I think the Merc designs have been fresh and nicely differentiated from the Fords.
Isn't that how it always goes- they put in a great effort right before killing it off (think Fiero, the whole Pontiac division, etc.)
P.S. Moon Unit got it's name because if it was jacked up with mudders it looks like it would make a great lunar rover.