Edited Dec. 20, 2017 at 8:02 a.m.
"Could Eichel want to be traded?" You bet. IMO, he had "signers regret", the moment he inked that contract. Not that I blame for taking 80m, but the reality is it looking bleak for the Sabres for the next four years. And then it still means that the Sabres will have to develop their next group of young players well to make a step towards playoff contention.
Not too many players have the "courage" to do what Trouba did two summers ago. Turn down a long term deal, and take a very modest two year deal. Leads to being a UFA, four yeas after his expiring ELC.
The trade: I don't think he would get all that, though it only takes one team to make the deal. Why? There aren't many good teams that have 10m cap space. So now you're looking at poorer teams, lottery teams, who might not want to risk so many high picks for one player. But here is the biggest reason why I think the trade won't fly. You aren't taking any money back in a trade. So a team could spend 10m in free agency, and still keep all it's draft picks. To me that could be a lot better (though maybe not) that spending 10m on one guy. Two 5m UFAs isn't as good as Eichel likely, but keeping the three first rounders and more, if I'm a GM I'd want want.
As you described why it's beneficial to the Sabres "but gets 3 1sts, 2 2nds and a 2C to really help the Rebuild." The exact same reason, why another team wants their picks, and the 10m cap space.
It's the same reason why don't see many RFA offer sheets. Teams have to spend to the players value and give up four first rounders for a premier players. Isn't to better just to spend that "premier player "money elsewhere and keep your four first rounders?