I inquired about the exact same thing and I also opened it up to the luxury wheels too. The day before my '14 GX arrived, my salesman told me he couldn't do the luxury. I think you just have to be lucky and find a willing owner. But for the f-sport wheels, I would have had to fork over an extra $900(minus tax) to trade my wheels(premium) in for the f-sports. The weird thing that I researched and pointed out is that the stock wheels are actually worth more than the f-sports per Sewell's parts website. They're like $500-something a wheel whereas the f-sports are now around $300.
Regardless, I declined because you can get a full set of f-sport wheels shipped to your door from a legit lexus dealer on eBay for $1200-1300.
But who knows....you might get that one salesman who's willing to do it under the table or you're a really valued, repeat customer.