You cannot have people inside the tube at the same time as vehicles are in the tube regardless, so there's no point to conducting maintenance in a vacuum; you would simply repressurize it (aka, open valves at the pumping stations, or the emergency exits). But there's also no point to ever having people inside. There's nothing except for an accident to damage the inside of the tube; the vehicles do not touch the walls, and it's a very rarified atmosphere, so it's not going to rust from the inside. If there's any need from maintenance, it'd be a need from the outside.
There is one thing that I fault the initial design for, which is the proposal of a two-tube system. This means that if one tube has to go down for maintenance, you have to alternate the other tube between directions, and each time you switch it, wait for it to clear. This would be a big throughput loss. With a three-tube system, you can have the third tube follow whichever direction has the highest demand at whatever point in time, and when one tube goes out you can still keep bidirectional traffic going. Maybe have the third tube be a "stop halfway then continue" design so it can offer service to the valley, at lower speeds.
The other thing I fault the initial design for was for setting it up as a competitor to HSR, which was obviously going to invite a lot of anger against them, and while most of it is just by idiots who never bothered to read the design document, some is legitimate - in particular, that Hyperloop doesn't serve as many cities, or city centers (which they really should have done), like HSR does. I feel that they should have proposed LA to Vegas as the initial leg, so as not to stand in competition to HSR, and so there would be few cities in-between. It's also raise the concept of Vegas magnates funding it; the ability of LA residents to hop to Vegas in half an hour for cheap would be hugely beneficial to them.
As for going into cities: I know they wanted to give a very impressive price figure, and going into cities would have raised that, but as it stands, their price figure was so low that a lot of people refused to believe it (without ever looking at why it was low). A higher price figure because of going into cities would have both made people more credulous, as well as being a more useful, likely-to-be-funded system.