The parties as a whole are rotted.
You don't fix a rotted floorboard, you replace it.
Throw out the corrupt officials.
You bring in now officials, ones who aren't driven by greed.
And, if they prove to be dishonest, you recall them as soon as possible!
You show the problem when the wrong metaphor is used.
The problem is that special interests are able to dominate the voters' opinions by selecting people who represent their interests, making donations needed to win that only they give.
Destroy the parties, throw out the incumbents, get new people - and you have done nothing to fix that, in fact you made it far worse.
Now elections are filled with new faces the public doens't know - who are beholden to the special interests to get selected, to get funding to be 'serious candidates' at all.
And when they screw the public, they're quickly out and it's on to the next special interest-selected and funded candidate who does the same thing.
If you can fix it for 'new' candidates, you can fix it for the current parties easier.
The effort to build a new and viable party is so hard that you are likely to do no more than a tiny effort that splits the votes with those you agree with most and elects opposition.
That's why the only party to get much attention at all winning primaries is backed (quietly) by corporate interests, Fox, the Koch brothers etc.
It's really more an extension of the Republicans presented as 'new' to get the votes of those fed up with Republicans.
You say 'bring in new ones not motivated by greed'. Greed is a very simplistic comment - they're usually more either 'for the people', or 'hired hands' for ideology/interests.
It's basically about competing interests behind the candidates - which interests can get 'their person' elected, using money, marketing, etc.?
What's to stop your 'new' faces from the same things as the old faces?