Buick is obviously trying to balance risk and reward, so to speak. It is trying to venture toward that zone you speak of (risk) but wants to be loyal to its core market (reward). While I am not the traditional Buick buyer in demographic terms, I am awed by the reliability of their vehicles and will buy another. Yet, I don't want to pony up $ 40K for a car since I don't have it...I'd rather be in the $ 25K range. Maybe the Buick line could handle a little bit of bifurcation with Olds being gone...that is, expanding it to anchor the Buick segment and the upper end Euro-touring sedan/crossover. Also, where do you strategically stop so as to avoid cannibalization between this and the Cadillac brand? That needs to be looked at.
Let's not be so harsh on the LaX and the Lucerne. They are very competent vehicles. However, the execution could be better. The LaX has some interior quirks that are old school (the mousefur, yikes) and the Lucerne, in my mind, has poor ergonomics up front which don't involve the driver the way that a touring sedan would. Still, they are leaps from what preceded them, so Buick needs to keep going. More provocative and innovative styling combined with the current levels of reliability would serve them well.
By the way, I had a LaCrosse for 1 week and 2200 km (1400 miles, more or less) in the Montreal area about a month ago and it was a very likeable car. Except for a couple of shortcomings (the fabric, the mousefur and that stupid ass grille up front), this is a great value for the money...that's my opinion.