As great as it would be to make the playoffs, once in, chances of winning a cup are still only going to be ~5%.
The correct approach to be methodical and always rebuilding until you have a top 5ish roster, then to go all in for the cup run. Just have an internal valuation (that shifts according to the market) for all your assets and make a trade if you feel that you have been given an offer that surpasses that valuation. If you are going to be a fringe playoff team that year, great, still trade them since your players will likely have inflated values because they have performed well during the season. Moreover, immediately trade your good, aging players after any sort of successful playoff run since their values will be inflated.
JT Miller is in his prime, having a great year and is the type of guy that will win games in the playoffs. Cool, but trade him if a team exceeds your valuation for an offer.
Demko is young, improving and already one of the best goalies in the league. Cool, but trade him if a team exceeds your valuation for an offer.
Hughes is a young elite number 1 defenseman of the type that you can almost never acquire by trade. Cool, but trade him if a team exceeds your valuation for an offer.
Yes optics are a factor here, and it is also correct to "say" that certain players on your team are off the table since that helps underscore your position on a bargaining table, but in reality no one for any team should be immune to being traded if the offer is right. The fanbase has an emotional attachment to Hughes, Pettersson and Demko and that sells tickets, but they would just as soon pay to watch 10 first round picks or whatever the crazy return would be for those guys.
Look at European soccer: Phillipe Coutinho was the best player on a team in title contention, beloved by fans and likely the best player in the EPL, but when Barcelona came along with an insane 146M pound offer for him, they just basically said: ok cool, I am going to bet on my scouting department finding 3 guys that will be just as good as him in the future with that money. Now, just 4 years later they are both a top 3 team in Europe and one of the most profitable in the transfer market.
You have to always want to improve and that will mean making tough decisions and ultimately trading some good players away.