supervisors don't know everything! so if you believe in it, go for it.
my first two projects that were given to me, were rubbish, both technically and otherwise.
but when i came up with my own idea with help of a visiting professer, my supervisor didn't really care. until i started to get good data. and now it's all forgotten how it all came about, and i wrote a paper and it got published on it.
so they don't always know
and the other project that he thought was great, it's been 5-6 years and it's still not working to the level they want.. i stopped working on it, and now it's a poor RA's headache and not mine!