I've seen way worse proposals; value isn't making me think "ARE YOU CRAZY??" or "the other fanbase is going to have a Sh*t"!, so Kudos. Mtl is also looking for a top 6 winger and this addresses that.
However, I think Mtl here says no here for the same reason STL would want #5; though Kyrou is a "known" value that can play now, the draft may be deep enough that #5 overall may have a higher chance to help a team in a meaningful way. At the very least, it may simply give STL a 6 years window to replace kyrou with, if a rebuild is in the cards.
I'd say no, but id definitely see if there is interest in other assets (mtl is especially loaded at D right now), maybe coupled with later picks.