When making the final cut of Blade Runner, they did something like that to fix a line. The line was one thing, but Harrison's lips said something different.
They fixed it by recording the line with his son, and pasting the result over Harrison's mouth and jaw. His son's facial structure was nearly a perfect match. I'm glad they did that instead of CGI, because no one has been able to a human face look realistic yet. It's always a little off.
Frakes is older and rounder now, so it wouldn't have worked. Upscaled SD beats bad CGI in this case.