I have no idea about the possibility of switching seats but I imagine you could do it as long as you didn't expect the ventilation to work. It would surely be $$$ regardless.

I have AVS and I actually think my seats are a bit on the firm side. I've gotten used to it and I love the ventilation, but I do wish they were a little softer.

Never done a side by side comparison of sport vs. comfort vs. ventilated though...

__________________
2009 E90 M3 M-DCT | Alpine White/Black/Carbon

SOLD: 2008 X5 3.0si | Black Sapphire/Black Perforated/Burl Walnut | Premium | Sport | Cold Weather | Premium Sound | Active Ventilated Seats | Auto Tailgate | Comfort Access | Running Boards | Heated Rear Seats | PDC | OEM 20" Style 214s | Titanium Kidney Grilles | Tint 20% Rear/35% Front | GP Thunder 7500K Halos | Xenesis Fogs