It does not make any sense to trade Lily for Andersson. We've put six years into him, and he is finally getting close to what we need. If we trade for Andersson, it should be to add him to a D core with Lily, which would give us two young, two-way RHDs.
That said, we should put a lot on the table for Andersson. He has two more years under contract and fits exactly what we need. I must agree with other posters though that trading Knies for him is nonsensical. Knies you keep unless trading for an absolute star, which Andersson is not.
If we use the Muzzin deal as a framework (1st, Durzi (promising second-round pick) and Grundstrom (less promising second-round pick), a potential deal could look something like:
To Toronto: Rasmus Andersson
To Calgary: 1st 2024, Topi Niemala, Roni Hirvonen, 3rd 2024. (Maybe not enough, because I think both prospects are worse than Durzi or Grundstrom where at the time)