Not very easy. Focal point needs to be dynamic and is very far away. Also the receivers are complex and not just a piece of mirror. Doable yes, but extremely costly. James Webb is nothing compared to a sun telescope
No, it is not. It is actually being seriously worked on by Nasa.
Also, they use the word "affordable". Now, in case if NASA this can mean practically anything, but there is chance it is not prohibitively expensive.
https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_...
Another reason to be bullish on SpaceX starship. Being able to send mass to space on the cheap opens up many new astronomical exploration avenues.