If you're putting a sleeve in, then brazing is also a possibility.

I'm wondering if one could make one's sleeve(s) loose enough that they could be pushed into the uncrushed section of tube. Then using a string, thread, or wire through he headtube and/or seattube pull them into place. Then braze into place. Welding is best with a tight fit, but brazing works well with a slight gap around the sleeve.