I'll start with the PP first--You can't throw anyone out there because what hand you are plays a significant factor in the way the power-play is set up. Eaves first unit is (and has been for at least 3-4 years) right-hand dominant. Corner guy (Lee) has to be RH, half-boards guy (Zengerle) has to be RH, point man (Simonelli) has to be RH, weak-side D (McCabe) has to be LH. Guy out front (Mersch) should also be left-handed so when he pops out for shots being fed from Lee he's in a one-timer position.
I've seen a lot of complaints about Kerdiles not being on the top PP unit. That's fine, but you're going to need to overhaul what they're doing. He's not going to replace Mersch out front. Replacing him with McCabe doesn't make sense either. He's cerainly not taking Zengerle's spot. If you insert him into any of the RH roles it creates passing lane issues.
As to your question on flipping Mersch and Barnes--The reason why I don't like that is because Lee and Mersch have worked really well together, and why on earth would you break that up? At some point maybe you have to, but I'm not willing to make the change yet. I'd be more willing to let Zulinick play with Zengerle and Kerdiles and put Barnes with Woods and Meuer. We'll see...I have a feeling that Zengerle line is going to bust out soon, and when they do...look out.