Pittsburgh is going to want a lot more than any team is willing to pay at this point.
I can see Pittsburgh making a shakeup, but I think it'll involve someone like Cole in order to get a center more than something involving Letang.
That's not really a shakeup though
I think if Letang gets moved, the Penguins would want back a replacement top-4 puck mover and a good and young 3rd line center. I don't think their ask would be ridiculous, I think if they got back those two pieces, they wouldn't make a huge deal out of getting back picks or prospects beyond that.
Some examples:
Letang to Arizona for Dvorak and Goligoski
Letang to Montreal for Danault and Petry
Letang to New Jersey for Vatanen and Zacha (not at all realistic, just using it as an example)
Letang to Vegas for Schmidt/Miller and Haula
Something like this as the base with adding the necessary pieces to that.