I'm an engineer (current job is designing and building small spacecraft), so forgive me for raining on physicists' dreams, but a huge reason such a telescope is not currently practical is the enormous amount of propellant required to get you there and then station keep to stay focused on a target. The latter is usually glossed over in this concept but it alone blows mission cost out of the water. Would make James Webb look like a cute little project.

If you don't have an active propulsion system for station keeping then you cannot pick targets. Who wants that? Nobody.

This concept is 50 years off at minimum.