While I have some skepticism with Aitcheson personally, I don't really see a reason to be upset if the Penguins do end up taking him. His upside is a lefty Trouba, which would be a great addition to the defense for the long-run.
The Penguins took Orpik #18 overall back in 2000 before the full-blown X Gen Penguins, I feel like Aitcheson this year would be really similar to that. He's likely not going to be a new core piece, but he should become a regular contributor and a supporting piece to your new core and brings a really unique playstyle that the team lacks outside of him.
Anyone they take this year will likely be that. If they take Eklund at #11 and Aitcheson at #12, those two guys will likely be the new Armstrong and Orpik for the next Penguins core. McGroarty, Koivunen and Brunicke are in that category too, they have good 2nd line/middle pair upside but just project to be complementary guys to the next core.