I don't think the hassle/airbag and seat heater compatibility/warranty issues of aftermarket seats on a NEW FiST is worth it. I doubt very much you can get a stock-like aftermarket solution for even the same 2k option price.
As far as warranty and hassles go, the very same could be said of ANY hybrid/BT setups, drilling factory hubs for 4x100 wheels, and any myriad other mods many do to these cars.
Besides, there are no seat heaters to worry about on the base cloth seats, just the air bag dash light.