I liked the idea of hanging on to Barnes and re-signing Holmes to a reasonable deal. Both are solid vets and I think HB plays better at the 4 so if Marvin were moved on it would only leave one starting position to fill.
Bagley clearly wants out and given his injury history and failure to improve significantly there's not a ton of argument for keeping him when the Kings would have to either lose him for nothing or try to re-sign him at the end of next season.
Buddy unfortunately regressed last season. He continues to be one of the best 3pt shooters in the NBA but he was a worse all around offensive threat, didn't attack the basket or draw fouls at all, and is still a very poor defender. Most of all, he's already shown that he's disgruntled as a 6th man (which appears to be his best NBA fit honestly) and Haliburton needs to be the starting SG.
All that said, I'm in favor of dealing Barnes if it improves the team and I'm not in favor of dealing Bagley and Buddy just to do it.
It really comes down to what the individual deal is and whether it improves the team. Does MBIII for a couple of mid 2nd round picks this year and next improve the team? Not likely, for a variety of reasons, including that the extra cap room isn't as valuable as being at the cap and gaining the MLE etc.
I get the idea of "we need to at least get something for him" but if Bagley's value in the league is really that low then one last year with him trying to play well to earn his next contract (likely from another team) is probably more beneficial in the short and long term than what those 2nd rounders might turn into. If there are good deals to make then make them, but don't jettison guys just to do it.
So, short story long, I don't really care if McNair blows this team apart completely or brings back everybody as long as it's the move that improves the Kings now and in the future. And we can only judge that by each individual trade, draft pick, or signing. We'll see what happens.