Knockout stages should always be single-match.
Think it only works as there's no spectators at the moment. Neutral venues would be a right pisser for fans to have to travel to each round. Having it at one teams ground would give them way too much of advatange.
Not if it is one neutral venue like we're seeing here.
I know it would never be 50/50 with all of the corporate but it would make for some great atmospheres imo.