GMs aren't doing their job if they're unwilling to even talk about the "untouchables" on their roster.
No player is truly untouchable. It's just that moving Kreider make no sense unless it's truly going to make the team better in the long run. Kreider is young enough to be a major contributor when this team is ready to compete again. You don't trade players like that without a very good package coming back. A chance at a player that could be as good as Kreider one day isn't enough, which means late first rounders and B prospects are pointless. You need either a young roster player that has a pretty good chance of eventually becoming as good or better than Kreider, or multiple blue-chip prospects, plus a sweetener, as an incentive to actually do the trade.
I think Nashville is a very intriguing option that was brought up. Tolvanen and Fabbro fit with what I'd be looking for if I was GM of the team. Nashville fans probably balk at giving up both of them, but that's the kind of quality I'd be looking for to move a guy like Kreider. If I'm not getting both of those guys, something else that's damn good needs to be in the package, because, while those players are absolutely blue-chip prospects, they're far from certain, and probably unlikely to become what Kreider is right now, and will be for the next few years.