(Before I get into this, I like using Byron Baders hockey prospecting when looking at prospects because I fully believe that forwards would put up a lot of points in their respective league also taking into account former players is one of the best ways to predict NHL talent. I believe in the eye test too so don't get on me too much.)
Alright, so lets dissect this entire hypothetical.
Erik Karlsson was really the last true player of this caliber to be traded and at the time of the trade he was 28 y/o which I would still say was his prime.
Ottawa recieved:
Unsigned rights to Josh Norris (Had 19 points in 17 NCAA games, which at the time would be considered pretty underwhelming)
Dylan DeMelo (Who at the time was very mid and was not the player we know today)
Chris Tierney (Was 24 y/o at the time, but still a 40 point player)
Rudolfs Balcers (Imo the best piece at the time had a good 20 year old season in the AHL)
Tim Stutzle (Was the first round draft pick in this trade, this was completely unpredictable, so I really don't want to include him, but that's what they got)
Mads Sogaard (2nd round draft pick, has not looked good in the NHL)
Zack Ostapchuk (2nd round draft pick, Has 86 hits but does not look good at anything else, funnily enough he was traded to San Jose)
Now, after looking at the return Karlsson got I would say that something similar for Hughes is realistic, but probably even more because he has put up generational numbers. I think people on HFboards and PuckGM create terrible trade scenarios by acting like teams will trade 5 players for another teams 5 players (has happened before, but not entirely common or realistic).
The best return for a player in my opinion was the Rantanen trade. He returned an A+ prospect who is currently in the NHL, two first round picks, and two third round picks. I think something similar is fair for Hughes.
Hypothetical from Buffalo if using futures and Vancouver wants a full rebuild:
Zach Benson
Mattias Samuelsson (Replace with Kulich, but I believe that Vancouver would want a LD, Samuelsson plays the hardest minutes amonst defenseman on the Sabres)
2025 First Round Pick
2026 First Round Pick
2027 Second Round Pick
This is somewhat similar to the Rantanen return except the Hurricanes got a much older prospect in Stankoven. The thing with Benson is he could take a huge leap since he's only 19, so honestly this is probably too much. The thing is you're getting back a guy who is putting up some of the best offensive numbers and playdriving results and also playing one of the best defensive games. People don't know this but Hughes has developed a defensive game over the last couple of years compared to Makar who hasn't sh7own any massive upgrade.
If Vancouver doesnt want futures:
Tage Thompson (Assuming Tage is a consistent 80 point player and not 100 point player)
Owen Power
2027 Second Round Pick
I mean you really have to think about it this way. Buffalo is getting a guy that they could pair with Rasmus Dahlin. This would be one of the greatest pairs in NHL history. Think of it as a modern day Ray Bourque and Rob Blake pairing. I don't see why Buffalo would do Dahlin for Hughes one for one.