the main concern would be the chain inner clearance vs the cassette sprocket width, which I think is only 0.2 mm different between 8 and 11 speed cassettes (saw it somewhere to be 1.8 and 1.6 mm respectively). anyone know if the combination would work?

reason why i ask is because I built my commuter bike based on the assumption that 8 speed chain would last longer because it's wider. It turns out the newer 11 speed chains are still pretty cheap, and they'll out last the older designed chains due to better design.