No one ever sits on my rear seats but with the premium package colour keyed stripes. I personally like the way the sets look back there. As for weight savings, not enough to bother with, IMO.
Plus on several occasions I have needed to fold the rear seats down to carry large/long items. You would loose that capability with the rear seat delete and x brace. It's all in what you what though.
OP, I would think long and hard about your decision.
-2012 Grabber Blue GT 6M Premium w/ Brembos, Glass Roof, HID security pkg, Rear Camera, 401a, FRPP GT500 Axle-backs, Front Pioneer TS-D6802R speakers, JHR bracket, Bondra clutch extension.
-1986 Mazda RX-7 GX - Fast Mirage 16" Wheels, Sumo Firenza 205/60R Tires, slotted brakes + performance pads. Otherwise factory stock.
-2008 Mazda Mazda3 GT Sport - Stock, 5MT.
-2004 Volvo XC90 T5 - Comfort pkg, safety pkg.
-1995 Infiniti G20 - Sold, Pioneer head unit, lighting mods, miss it dearly.