Not sure I follow.
1. Don't do anything illegal. Talk, and if you feel you're close, say "ok, let's finalize after expansion draft". There are ways to do it without it being illegal, basically
2. What can Seattle do with a UFA at the expansion draft? My understanding was that they are ineligible. Can they select an unsigned/unprotected Danault from Habs? I thought they couldn't. Or could they select him, only to lose him 7 days later if they don't re-sign him (when he officially goes UFA)?
If they can pick him unsigned/unprotected - that's news to me. They're not allowed to negotiate with him, as he belongs to the Habs. So they'd have to draft him and only after negotiate with him, and hope he signs. That's a hell of a risk they'd take. I just don't see it. But if they did that - and if they did offer him a huge contract - well that's a risk we take. Maybe Danault still waits till UFA date to sign with Seattle, to see if Habs match/surpass (I assume he'd like to return), maybe not.
Whole Danault premise aside - Drouin is a huge question mark based on why he left/how he's doing/if he's even capable of going back to the NHL next year, and to Montreal specifically. If he's ready to return to Habs at 100% next year, I can't imagine Habs paying to get rid of him, he's still valuable. If Seattle can take him for free, they would in a heartbeat (assuming no health concerns).