Big risk for Vancouver, where given his age...it's entirely possible that this is the start of Reilly Smith "falling off a cliff" in his play. That $5M becomes really problematic next year if that's the case and the "change of scenery" doesn't get him going again.
Whereas Mikheyev, i think it's more likely that he bounces back with more time to recover from that knee injury that does seem to be still hampering him a little bit.
I've always really liked Smith as a player though, and he's a solid enough 2-way player to offset a lot of what they'd be giving up with Mikheyev. So a swap is at least vaguely worth considering here. But i'm still really hesitant. Especially at the cost of a 2nd round pick. That's too rich for the amount of risk if he doesn't bounce back. Even if there is decent "upside" if he does get rejuvenated.
I also happen to think Mikheyev is getting dragged a little bit excessively by a lot of Canucks fans at the moment though. He happens to be in an extended scoring "slump" that is drawing a lot of ire. But he's still a strong 2-way player and realistically, slumps and hot streaks tend to characterize ~20G Middle-Sixers like him. So i think a lot of expectations are kind of misaligned on him. He could score a bundle of goals in the next few games and people would probably overcorrect back the other way.