Nah, man, you're not crazy, but it isn't original either.
Back in the '60's and '70's, a lot of guys made their own mini-bikes by attaching small motors to bicycles.
Of course, the idea goes back to the 1930's and was the birth of the Whizzer bikes and what became motor bikes.
Maybe the use of a chainsaw on a mountain bike is new, but the concept is not.
Frankly, the older designs looked safer than the motorized mountain bike shown on the page you advised. Those exposed chains are going to bring a quick end to somebody's bicycling career when it tears their leg off.