it works - yes.

And you can upgrade, using LH miles&more miles (or vouchers) any fully paid fare (as long as the flight is LH# and LH-metal).

On the other hand, LH 'releases' seats, in business-class for awards and upgrades, often only 2-3 weeks before the flight. MIA, being more a touristic than a business destinations for Europeans, I would be very optimistic in getting an upgraded seat later.