You may as well take the energy used for the pneumatic system and put it straight on the train. The main issue with a high speed train in the open is the possibility of derailment and fact that it's just open to the environment. Wild life etc can cause big issues.
I think a compromise for the hyperloop would be to have a tunnel (under or above ground does not matter) that makes a literal loop, maybe one per province, and it covers all the major geographical locations, and has stations that are evenly spaced. All trains would depart and stop roughly at the same time. That way each train just pushes air while the next one pulls air. There's obviously still going to be a lot of static pressure, but it would probably be half decently efficient vs if they all stop at different times. There could be various air vents too, that would be an engineering feet to some degree to design them effectively while ensuring nothing can get in, but it's doable. But either way having them all take off/arrive at once means they never have to stop for others. The train itself does not matter too much how it's designed (rails, wheels all around the tube, maglev etc) but the idea is with the tunnel you can travel at a relatively fast and constant speed without risking hitting anything. It would probably be cheaper to operate than an airline, so it would ideally be cheaper to travel on than an airline (at least that would be the point, it needs to be affordable to use). So what would take you say, 8 hours to drive, you could do in maybe 4 with this train. It would essentially be an alternate way to travel far while being cheaper than flying. Not sure how sound my idea really is though but it does sound more reasonable than some of these ideas. Sometimes you need to compromise instead of going for crazy stuff. Say the real hyperloop is built and works, how much would it cost to maintain and cost for passengers vs flying? Probably a lot. If it's the same price or more expensive then people are just going to fly. I think if anyone wants to "revolutionize" travel, it needs to be a system that fits right between driving and flying in terms of speed and cost.