To take 100lbs off the car, roughly equivalent to 10whp in terms of acceleration, you would have to remove spare tire+Jack (40lbs), get lightweight wheels (roughly 35lbs if you go LIGHT), and then a lightweight battery (not super reliable).
For all that you'd be spending near $2000. The wheels will be around $800 - $1500 themselves and then you need tires because you will probably be going to a 15" wheel or at least a 16" wheel. That's another $500. The battery will be $200 - $400. Just doesn't make sense to spend all that money for 100lbs.
As concerns the bolded above; there ARE very lightweight, but also FULL power/capacity batteries out there (lithium).
The problem, which I hinted above, is that those batteries and their specialized chargers cost WAY WAY MORE than what you quoted for the current lightweight, but MUCH lower capacity/current, AGM batteries.
I basically agree that it would be less coin to throw power at this platform than to significantly lighten it.
But as Jeff stated above, there are so many other benefits to losing weight
besides just better acceleration <-(in some cases).
The one he did NOT mention is the reduced stress/added reliability on the whole drive train/unibody from lower weight
regardless of the power output of the engine.
This is the criticism I always levelled at the f body peeps who added 300 lbs. of infotainment equipment to an already heavy, loaded car, and then threw 800+ rwhp at it with boost and spray, and wondered WHY they were ALWAYS breaking even supposedly strong, aftermarket rear axles, and built transmissions/gearboxes.