Edmonton adds Zadina and Namestnikov in an effort to boost depth scoring and not waste another year of prime McDavid and Draisaitl (Holland also trying to save his own job). Zadina is a cost controlled buy-low add. Holland drafted Zadina due to his high level scoring potential and by putting him on a line with McDavid or Draisaitl it give Zadina his best chance to reach that potential. Edmonton also gets out from under Smith's 2023 contract and adds some depth on the blueline.

Detroit takes on 3 cap dumps as an extra cost to add a potential 2C/3C in Holloway and a top4 LD in Broberg.

With that said, who would have to add and how much to make this work for both sides?

I'm gonna be honest, I'm not even sure EDM counters, cause their not getting any real upgrade value.
Griess isn't an upgrade on Smith
Stetcher doesn't really do anything for this team
They're not going to give up on Holloway and Broberg for a return of Zadina
namestnikov at 50% retention would be nice, but that probably only gets DET a 3rd.