They already kind of do that, though. There's a wide range of opinion in both parties: in the Democrats, from social democrats to social conservatives, and in the Republicans, paleolibertarians to neofascists. Of course, there's often a bend towards supporting or opposing the current president depending on the political party, but it's not to the point where you have to conform to a certain viewpoint to get ahead in a party.
Her party perhaps, but Le Pen herself isn't a Nazi like her father.
And if we dismantle the parties without the system, new ones will arise and prop up the system instead.