Pie-in-the-sky impractical idea. Nice video though.

Do you have anything better?
Redecorating old tube? Even if they will fix it, it will still be
crowded, tiny, and hot.

The only other real long-term solution is to dig a new underground with
at least the same scope as the current tube (and preferably even
larger, including south). But I'm sure it won't happen in our
lifetimes.