I've also been pondering the RC lawnmower idea Dafni.
In the form of a mower deck that sticks out in front. Built out of 1/8" aluminum plate, powered by twin AXI 4130/20 outrunner motors, it will use 4S lipo along with a pair of airplane ESC's.
The batteries that power the mower deck will hang over the rear to act as a counterbalance.
I was first thinking about using a pair of carbon tipped 7 1/4" circular saw blades, but then began to imagine bad things happening. LOL
Instead of saw blades, how about we use a pair of these?