This move only happens if Sid initiates. If that's the case it's not going to be an open market. He's going to tell them "trade me to x".
Because of that, the return will not be anywhere near what it would be in a vacuum, and the right thing for the Penguin to do is to grant his request because of what he's meant for the franchise.
This is going to turn out like a house that's "for sale by owner". When that happens, a person looks at what they are selling and expects to recoup all the money, time, and sweat they put into a place. They don't see all the stuff that the potential buyer sees as crap they want to tear out and replace. They usually get less than what they think they should have.
If you think you are getting 3 1st rounders for a 38 year old Crosby, I think you will be very disappointed.
Personally, if I am a contender, I can't take an 8.7 add without something happening. I need you to take back at least that much or hold 50%... If you take cap dumps, I can consider extending Sid for another 2 years, which might get you 2 firsts. Depends on the franchise and of the owner thinks adding Sid puts assets in seats and merch out the door.
The guy has been such a thorn in my side over the years, I gotta admit I am savoring the demise of the Penguins. Ultimately, I can't see him riding out this downward spiral. What you get by moving him is the closure you need to turn the page and move on. After that you can go get returns for Geno and Letang. Admit the Karlsson thing was a bad plan and recoup your losses there.
In the end you need to decide what maximizes your return. In the off season, a team can make some moves but need to fit him in all season. Or you wait and make him the most a
highly anticipated rental player of all time.
Or you just let him get dusty and fade away into history.
Should be fun.