Here's my guess. Blade doesn't have special meaning here. The car is being compared to a blade, like a sword blade. Blades can be "wide" or thin, and "low-slung" makes be think of a sword that's hung (or slung) on one's side so that it's low to the ground. I assume the car also rides low to the ground. I think the metaphor continues by saying that the doors "scissor" towards the sky. This also references the name "scissor doors". And the body is designed to cut (= move quickly) through the air, like a blade.
There's also a possible bullfighting reference, as apparently Lamborghinis are named after famous fighting bulls. From Wikipedia
The Lamborghini Aventador is a mid-engined sports car produced by the Italian automotive manufacturer Lamborghini. In keeping with Lamborghini tradition, the Aventador is named after a fighting bull. Aventador (pronounced [aβentaˈðoɾ]) earned the Trofeo de la Peña La Madroñera for its courage in the arena in Zaragoza, Spain, in 1993.