I flew DCA-DTW-LAX in late June on a Friday night (last flight out). I'm FO and I made my companion a new SM acct when booking our tickets together.
She could check bags for free since our PNR was together. There seems to be no problem with this at all, especially if you go up to the counter for the First Class/SkyPriority/FO check-in line.
We were upgraded for DTW-LAX on a 757 w/live TV. We were only confirmed two hours before the flight which I was surprised about.
So maybe there's hope for you... good luck!