Well what if instead of making a single tube/tunnel (well it would still be a single one) they instead had it broken up int sections with airsealing doors? Yes complexity just skyrocketed but its a potential solution to the vacuum problem which is that instead of removing the extra gas from 1 large tunnel you have a bnch of smaller tunnels/tubes where you remove a smaller amount of gas from. This also has the benefit which is if there is a leak in one section and it can't be controlled then leading up to it they could slowly increase the air pressure and then past that section they can work to decrease it.

I want people to be creative.