I'm not saying Trouba couldn't be #1D
There have been many statistical articles showing that he's plays in an equivalent manner to a #1D. These two charts just skim the surface.
As for contracts, I think there is a potential for Buff's to become a problem if they want to keep everyone and especially if they are looking into acquiring that much needed second line center (assuming Stastny will be gone after this year).
His contract moves from a NMC to a 14 team NTC next year. He's movable. I don't see this as an issue.