Let's say you just do Maatta, Sheary and a 1st for O'Reilly. That likely leaves the Penguins with something like:
Guentzel-Crosby-Hornqvist
Rust-Malkin-Kessel
Hagelin-ROR-Simon
Kuhnhackl-Sheahan-Archibald
Dumoulin-Letang
Cole-Schultz
Hunwick-Ruhwedel
From what I see in this lineup, these are the big issues I see with this roster:
1. Ideally you have a better 2nd pair LD than Cole, but then again, that pair worked well last year and it's very possible that pair could work again this year
2. Ideally you have a better bottom pair RD than Ruhwedel, but then again, Hunwick-Ruhwedel isn't a bad pair. It's just an okay 3rd pair
2. Ideally you have 2 better wingers than Hagelin and Simon on your 3rd line, but then again, you also have players from WBS that you can try and it doesn't matter who the wingers on your 3rd line are that much because you have a 1st line center as your 3C.
The defense can survive with that move, and if you have to, I think you can address the 2nd pair LD spot via trade, similar to how the Penguins added Hainsey last year. Your 3rd line wingers can probably be fixed internally, and even if they can't, I don't think you need to get that good of a 3rd line winger to fix that 3rd line, since ROR is so good.