Miles & More (Lufthansa, Austrian, Swiss, and other partners) - Upgrade suggestions for Div Miles Award on LH

I am a LH Senator living in Europe motivated to use several hundred thousand USAir Div Miles sooner rather than later due to expiry, bankruptcy threat etc. After unsuccessfully exploring availability of business class award RT on LH between Franfurt & Miami through both M&M and Div Miles programs, I ticketed economy class award using USAir Div Miles. Any suggestions for getting an upgrade to bus or 1st. I don't mind spending some miles but think it will be gate agent in Frankfurt that makes the difference. Can Senator lounge staff accomplish this? Are they any more likely to help?

my understanding is, that reward flights cannot be upgraded. and if you want to upgrade a payed eco ticket, you need availability in the desired class (and this is the same stock like directly reserving a business class seat).

...business class award RT on LH between Franfurt & Miami through both M&M and Div Miles programs, I ticketed economy class award using USAir Div Miles.
I don't think there is no way to upgrade an award ticket. I would not use my miles for an award in economy class for a long haul. Why don't you look for another LH gateway from the US? For example, you can try to take FRA-PHL in C or F. Why do you restrict yourself FRA-MIA nonstop?