I know it's usually done with traditional buttercream, but I was just wondering if it's possible to make flowers out of smbc ahead of time and let them dry before placing them on the cake.

ASure, if you've figured out a way to make a stick of butter dry rock solid :D. Otherwise I'd say you're barking up the wrong buttercream.

AYeah, I don't think SMBC really "dries". At least I can't imagine the SMBC I make drying in the way ABC flowers do.

Not really. I mean, if you handle them carefully and let them set up on parchment in the fridge, and work quickly when you put them on, and I mean QUICKLY, I suppose you could. 

AYou could pipe the flowers, allow them to set in the fridge and then apply them to your finished cake while they're still cold and firm. But they'll never be 'dry.'