First off congratulations! If you are like most of us here, you will love the car.
Now to your question - I guess if you only hauled cargo and never needed the rear seats that would be an option. And while removing the seats would give you more space, I'm not sure the weight savings would provide any significant performance gain.
Consider the following:
We know F= m * a and thus a = F/m
From this we can see if we reduce mass by say 10% we will improve acceleration by 10%. And since V = a * t, our 0-60mph time would also improve by the same 10%. Range, on the other hand, would improve by a much smaller margin since accelerating the mass is only part of the problem (vs fighting wind and road resistance). But lets ignore range for the moment (even though that is what we care most about) and look at 0-60 time (since it is easier to analyze in this case).
The FFE weighs 3624 lbs and does 0-60 in 9.5 sec (or so says my Google search). A 10% weight reduction would mean loosing 362 lbs and would improve 0-60 by ~0.9 sec. Removing rear seats might gain you 50 lbs or so. With lighter wheels, a LiPo 12V battery, rear seats gone, and a few other mods you might get 100 lbs or so. That's a 2.8% reduction, or 1/4 sec off the 0-60 time. Big improvement if you are drag racing, but probably meaningless otherwise.
Oh, and just for grins, the ST Focus does 0-60 in 5.9 sec. You would have to remove over 2000lbs from the FFE to match that figure (assuming weight reduction was the only improvement you could make).
