We could argue back and forth about who that star could be, it could literally be most players in the NBA. Then talk about fit with Giannis, like the 13 other players on the team don't matter. Adding 36 yr old No shooting Jimmy Butler to 37 year old Steph curry, 35 year old no shooting Draymond Green, and 23 year old no shooting Kuminga, perfect fit for Butler? Fox is just an example to show with star, Giannis and Matas, we likely have three stars and still have some cap room for a fourth good player. If Matas is star level. If.
Butler is still a questionable fit. Why do you think the Warriors were interested in Vuc and other shooting bigs like Horford? Why do they start Draymond at center? Butler was the best target they could get, and it helps that Butler is really good and very smart as well. Kuminga doesn't play and the Warriors don't want him. The only reason they're keeping him is for a trade. Also helps to have the greatest shooter of all time.
All these equivocations are just that, Kyrie is a bad looking fit with Luka, Garland is a bad looking fit with Mitchell. Two guards that are minus defenders in the first case, two guards who are small in the second. Lebron is a bad fit with Luka. You want to focus on fit over talent, because Fox is arguably as talented as Holiday and Middleton, those combinations are bad fits. You're not coming up with a reason Kyrie and Luka are a good fit, or Mitchell and Garland are an ideal championship backcourt. How about Bradley Beal/Devin Booker? Did the Suns pay a lot to put that backcourt together?
There is evidence of Kyrie playing next to a great point forward in Lebron and succeeding. Kyrie has experienced playing next to another star who needs to ball. He had the shooting and overall offensive skillset to make it work. The concern for Dallas is building the rest of the roster with enough defense.
Cleveland already had Mobley and Allen to support Garland and Mitchell defensively. I'm on record here saying that the Lakers trading for Luka didn't increase their chances of winning a title. That trade decimated their frontcourt and defense. It did give them a future after Lebron leaves which is why they did it.
Trading all those assets for Giannis only to build a poor supporting cast around him is stupid. You should be concerned about fit, that's how you avoid the mistakes the Suns made. The most expensive roster in NBA history and not a single playoff win. Sure, let's pair Giannis with a guard that isn't a good defender, can't shoot 3s, and also wants to get to the rim.
The Suns were one of his preferred destinations from the beginning, they also showed the most interest until the Warriors got desperate.
If Giannis asks for a trade it will likely be next summer when he'll only have 1 year + a player option left. Giannis has the option to bolt in free agency, which gives him more leverage.