Simplify/reduce rhythms

For example, let's say a song originally uses eighth notes as its smallest beat division. The easiest way to notate it would be with eighths and all the other rhythms would be relative to that.

Now, suppose I want to have this piece available in a simplified form. The relative rhythms would be the exact same, but instead of eighth notes, we would have quarter notes; instead of quarter, half; etc. To be played in double time, so that the score is more readable but sounds the same when played.

If there is a shortcut to do this, I haven't found it myself. Currently all I can do is manually rewrite everything from the beginning.