I did not know Gostisbehere was a future hall of Famer, the next Peter Forsberg
At the time of the Lindros trade, they didn't know Forsberg was going to be the best player in the deal, either. Meanwhile, we already know Gaudreau isn't arguably the most impactful player in the league, which Lindros was until his brain was scrambled into oblivion. We already know Gostisbehere and Schenn are excellent players, and you're talking about Philly adding in our most recent #1, another talented defenseman, and a future pick for a player not immensely better than who we're already playing at his position (Gaudreau's better than Jake, but not by enough that it's a desperate need of ours to upgrade), a good prospect (which is as far as I'm willing to go with Shinkaruk) and the opportunity to substantially weaken the position we most need to improve.
Your suggestion is bad, and you should feel bad. Want more to move Gaudreau? Ask Buffalo, or better yet, ask different teams entirely. Philly doesn't want the original deal, let alone your attempt at highway robbery.