Maybe Mr Hancock can give a better opinion of Oiler needs, but I think 13m a year could be better spent on other UFAs (or not spent) than Buf and Lucic.
That's a lot for Panthers to give up for Pouillet. Maybe they could just sign a UFA and keep their picks.

I don't care about the return. I was just trying to get his salary off the book to free the cap space needed for Lucic.

I think they try for Lucic because of Chiarelli, not that they necessarily need him.

This summer there are only two big free agent defenders potentially hitting the market - Buf and Gologiski. Don't think there is anyone else who can move the needle. Hamhuis and Colburn are a rung too low. Maybe If that's true, then the Oilers need to sign Buf. They can't let this defence continue as is.

Lucic and Byfuglien absolutely address the size concerns that the Oilers have with this current core but the downside to this is that you are leaving little cap space to re-sign Yakupov, Draisaitl, Nurse & McDavid.

It's a catch 22

I think its manageable. This model starts with $6M in cap space. If the cap goes up $1M per season, that's $7M next year and $8M when McDavid's ELC comes up.

Hendricks should be replaced by a player on a $1M contract, savings $850K
Fayne gets replaced by Reinhart, saving $2M to $2.5M

That's about $11M, plus the current base salaries of $2.5M + .98M + .93M + .87M = $5.5M for $16M. Let's say McDavid gets a Crosby $8.5M, that leaves $7.5M for Draisaitl, Nurse and Yak. You are going to end up trading one of Nuge or Eberle to free up cap space which bumps you back up to $13.5M to sign Draisaitl ($6.5M) and Nurse (Klefbom deal around $4.5M) which leaves a little money for Yak. If Reinhart plays well, you move Sekera and you have additional cap space to play with.

It's very tight, no doubt, but it could be managed.