He's already played with Chabot on a regular basis & I imagine he might again as well, why wouldn't he? Given how much ice time Chabot gets it's also likely that Chabot will split time with Zub & Zaitsev too as he does now. I think they will want an experienced D like Zub or Zaitsev to spend some time with Sanderson until he is aclimized to the NHL.
It's been two or more yrs that they needed to bring in a top 4 RD & look how that has gone. With Sanderson coming I doubt they spend very much on a top 4 RD, if they can even get one to come here. They could have two in waiting in Thomson & JBD, they just need one to take the next step & at the moment Thomsn seems closer.
It's already a soft defence core & if you add another small soft player well IMO it gets worse & they get physically overpowered. And given the history so far of this coach I think it's much more likely he goes with a big physical guy back there to handle some of the rough stuff & play the PK.
I think the team does need a top 4 D but likely will not sign or trade for one.