I've been thinking about it this way:
Is Fox/Murray/Sabonis a good enough core to seriously contend?
If not, then maybe the conversation should be trading one or more of those three as part of the needed "upgrade" to get this team to the next level.
But if you believe it is, the Kings shouldn't need a fourth "star" per se, but more of the type of trades that transformed Dallas at the deadline this season.
They struck gold with Lively as a rookie, signed some useful (also long and athletic) vets in Derrick Jones Jr and Dante Exum, but made the biggest push after trading for Daniel Gafford and PJ Washington. Also, big kudos to Nico Harrison for trading away Grant Williams in the Washington deal. Williams was the Mavs big splashy free agency move over the summer, and often GMs aren't willing to admit mistakes that quickly and move on.
But the Mavs did and they made changes to benefit their two star guards in Doncic and Irving, but surrounding them with big athletes who can defend and be vertical threats. They absolutely killed the Timberwolves but just running those staggered screen sets over and over and leaving the defense with no good option when Kyrie or Luka was left with a favorable matchup, a rolling big and a corner 3pt threat.
So what would the Kings need to do to fill holes and improve their roster around the strengths of Fox, Murray, and Sabonis?
They need a similar infusion of talent at the PF spot that Keon Ellis provided at the SG. They don't need another major scorer (IMO), but they need someone who continues to transform them defensively while being good enough offensively to command some attention. They need a better backup center. They need more defense and shooting in the second unit overall, and they need some length and athleticism.
I've advocated for some of these moves in the past already, but this would be MY off-season blueprint if I were trying to build around our current trio:
1. Re-sign Monk. Yes, this is easier said than done if a team decides to offer him a huge money deal. But it's not a coinidence that the team's playoff hopes went down at the same time Malik did.
2. Pry Jonathan Isaac out of Orlando and gamble on him staying healthy. He's my ideal fit between Sabonis and Murray.
3. Send some future draft capital Portland's way along with HB and get Thybulle and Robert Williams to bolster the Kings bench.
4. Dangle Davion and #13 to move up in this year's draft a few slots and grab a big two way wing in either Risacher or Salaun. Neither will help much this season, but one (or both) could be a pseudo MPJ type player (likely not as good offensively, but better defensively) for the Kings in a year or two. Maybe two or three in Salaun's case. I think both guys are somewhat boom or bust, but especially for a team like the Kings, you have to take some gambles like this. Given that I'm not sure who else would need to be moved (along with future picks) to make get Isaac, I'm not sure who would be left on the roster, but this (or something close to it):
C Sabonis/Williams/???
PF Isaac/Lyles/Salaun or Risacher
SF Murray/Huerter/Edwards
SG Ellis/Thybulle/Duarte
PG Fox/Monk
to me is a team that is upgraded around the three core players. I have us moving Barnes, Mitchell, Vezenkov and Jones but maybe Huerter is dealt and we keep Colby. I haven't tried plugging most of these into the trade machine to really hone them in.