He's already been a legit top pairing defenseman though, or at the very least an excellent #3. He's having a down year which is the reason it's even conceivable we could acquire him but we have proof of concept that he can perform in top pairing minutes. It's not just potential. Assuming this continues, his down season can also help us get a bargain on his next contract.
My view of it is that if the left side of our defense in 3 years is KAM, Dickinson and Schaefer in whatever order then it really doesn't matter who's playing RD (assuming Dickinson and Schaefer hit something close to their projected ceilings). Sign or trade for some middle pair guy, hopefully develop someone like Pohlkamp into a bottom pairing option and fill the final top 4 hole at the trade deadline when we're ready to contend.
If we don't get Schaefer and/or Dickinson "only" becomes a middle pairing dman then we'll be even happier we acquired Miller.