I might like to see the Brewers use both McClung and Parra in a co-starter situation, with the other becoming a swing man.
1. You could play some matchups (lefty-righty) with opponents.
2. I don't think they want either to be up around 200 innings given their history (age or work history). This would give each a chance to keep the wear and tear down so they could ride the hot one down the stretch.
3. I know people are going to scream about not starting Manny full time, but his numbers are due for some self-correcting. He has been lucky to a degree based on some of his peripheral numbers, so I don't think he is quite as good as he has appeared recently, making him a candidate to move into this sort of swing role.
It would be a novel way to handle the situation, though obviously unconventional.