I think most GM's would know which teams 2nd round pick they feel will be highest. We didn't see "in division" premiums with a lot of deadline deals last year, I think you are blowing that out of proportion, big time. If this was a guy with 3 or 4 years left on his deal, yes, you want him in the other conference if you think he is going to hurt your team. For a rental, you just take what you feel the best offer is. Maybe pick a team ranked a few spots later if you really want to put the screws to a division rival, but it isn't standard for teams to trade extra for rentals like you are suggesting.
As per supply and demand, I would be shocked if more than 3 1st round picks are traded this year. This is an incredibly deep 1st round. I'm sure there will be plenty of teams interested, but again, this is Luke Schenn, not Cale Makar. Just because a lot of teams might want the guy for a 2nd round pick doesn't mean any are going to bid a 1st.