The advantage of a wholesale change is the chance to put a fresh face on the party. The downside is that the political community might read it as a sign of worry.
At the depths of the '82 recession, Reagan looked like a goner, but the economy came back and so did Reagan's fortunes? He stayed the course. Had he faltered in his policies in '82, we might not have seen as much progress in '83 and '84.
At the moment, a lot of people regard both major parties as unattractive. That's partly due to the polarization of politics. The Democrats might be a little too liberal and the Republicans a little too conservative.