Its clever, but for me the whole point of running a petrol engine is to get the 30min + run times. Converting to battery we cancel out this benefit and reduce it to nitro run times.
However, you could run without the noise hassle, and the cost would be offset to a point by selling the engine etc from you kit.
I think Brushless and Lipo is perfect for 1/10th, 1/8th is pushing it but for 1/5th we need another 3-4 years for the tech to get cheaper.