I tried that with my old spare grill, faile and threw it in the bin.
I tried to cut the middle, it's easy but where it joins in to the sides that is hard to cut. Then you will have to filler it and smoother out to make it look better.
Don't want to sound bad but go for it, you got the grill so cheap so you've got nothing to loose.
cheap mesh (some honeycombe) desposable bbq. remove mesh and prime then paint (stop it going rusty), i have used this many times (must be unused bbq) £2