The salaries would work in a deal like that, Ariza to LA, KCP to Philly, Fultz & McConnell to Phoenix. The only issue is the December 15th date. Trades must be within 25% of a players salary so they don't need to bring back a full $15 million for Ariza but they need to bring back an amount that is within 25% of it. Fultz for Ariza straight up doesn't work but if McConnell was included then it would. Salaries aren't the hold up. Philly may like McConnell because he's a fan favorite but they are legit contenders this year and they can't think about placing importance on fan favorites over guys that could help them make the finals and potentially compete with the Warriors. If Ariza returns to who he was in Houston last year, he'd help them in that regard a lot. A lineup of Simmons, Reddick, Butler, Ariza, and Embiid might be able to cause problems for the Warriors, depending on how well Boogie fits in when he's healthy.
https://basketball.realgm.com/tradechecker/saved_trade/7142051