No.

If I’m BUF I would absolutely do this

That is a drastic overpayment for Smith.

*underpayment

Lol

It’s a quality trade that helps both teams.

Ok but Vegas has no reason to make this trade. This makes them worse defensively and offensively.

Ristolainen doesn't make them better defensively (an area where they're already strong) and you're taking away a strength for them which is their forward depth.

Vegas d is very shallow. Holden and Merrill are playing prominent roles, and Tuch steps into Smith’s spot when he returns. It makes sense for both teams.

I agree. Their defense is very shallow and right now Theodore, sorry all the time Theodore is not producing enough offense for his type of play. Ristolainen would most certainly help their D and their power play significantly. Tuch would easily replace Smith and they still have Glass.