Your comment is very on point. If they slowly even out the atmosphere, they loose the speed. So they'll need to coordinate the door opening at exactly the right moment. And if it doesn't the whole instillation goes boom.
I feel like it would be better just to use the money to buy more rocket fuel at this point. This is so much alike to "game changing ideas" like the hyperloop, solar roadways, and other "disruptive" tech that make a cool headline, but break down the second you think about the real world logistics and cost.
I hope they prove me wrong if they can get it to work though, cheaper space flights could help the world in so many ways.