A second All-Star would be nice but I struggle to find one at the right price, age, contract, and availability level.
Maybe you can pull off a deal for an "Almost All-Star" like MPJ, Trey Murphy, or JJJ (that contract is rough though), but it's unlikely you'll find a deal that makes sense for both sides.
At this point, I'd be happy just adding more two way players. Give me a couple guys who can BOTH play defense AND hit a three and you probably have a real contender. Ideally they would replace the minutes you're giving to guys like Ivey and LaVert (and/or push Tobias/Duncan to smaller roles).
There's a lot of Herb Jones talk right now and he would be a great start even though his 3-ball has struggled a bit this year. Having a PG like Cade would probably fix that.