I would choose option C because of the following reasons:

-Upgrade to F potential
-Book on LH website and you may get UA 901/900 on one of the legs if price does not change
-For a person to be even considering a $3500 plane ticket, money is not the *primary* obstacle here.
-$3500 is a great Z fare to Europe any time of year, but in the summer, it's awesome
-50% EQM bonus
-$1500 is a *very* expensive coach fare. I saw that fare myself, and it would pain me to sit in economy for 10 hours after dropping $1500
-The biggest reason: no anxiety for the next 6 months thinking, "Am I gonna be in 10 hours of misery or 10 hours of comfort?"
-Guarantee seating next to your sig. other, SWU's on economy may put you apart in C because of close upgrade.
-I would not worry about BIS on UA metal for MM because by the time that happens, UA may not be around anymore...
-Life is short, live it up!