An interesting perspective, but difficult because Egypt is right next door. No matter what, this is going to remain a threat. The most obvious shot is to have Magas' invasion of Aigyptos succeed (at least to a greater extent). Background: Magas was the son in law of Ptolemaios and was appointed governor of Kyrenaika in the name of the Ptolemaic dynasty. But he declared Kyrenaika an independent kingdom in 276 BC, married a Seleukid princess, and thus betrayed his master. His subsequent invasion of Ptolemaic Aigyptos failed utterly, however. If in this ATL it is more succesful, we can see a bit of a crippled Aigyptos (possibly with the Ptolemaic dynasty overtrown), and a kingdom of Kyrenaika on the rise. Unfortunately, by that time, the fascinating hedonistic philosophical school had already fractured and was pretty much dead.
A more drastic and slightly earlier possibility is "no Alexander" (or "Philip lives longer"), which would allow for an alt-invasion of Persia by Greek forces (either later than on OTL by united poleis, or at roughly the same time by Philip). We may presume such an invasion would not be as uniquely ambitious as Alexander's was in OTL. Perhaps Anatolia and the Levant are taken, but Aigyptos gets to be an independent state? Few Greeks there at the time. I don't consider it unlikely for the Greeks to make Aigyptos an iondependent ally in echange for preferential treatment of the few Greek colonists living there.
We may reasonably project a period of Greek in-fighting after all this. Let's suppose an ATL where Philip kills Alexander during one of their OTL fights, and Olympias is either killed too or exiled. As a result of butterflies, Philip lives longer than in OTL (let's say the altered court politics stop Pausanias from murdering him), and invades Persia. He takes Anatolia and the Levant, and ensures the independence of Aigyptos. Note that Kyrenaika remains an independent republic through all this.
After Philip dies, a succession crisis of some sort emerges, and the city-states down south revolt. The Persians take back Anatolia and the Levant, but the (native-ruled) kingdom of Aigyptos (well... Kemet, I guess!) is too difficult to re-take. A protracted conflict between the Persian empire and the kingdom of Kemet drags on, weakening both. At the same time, Makedon is destroying itself in civil war, and while the Greek city-states have gone independent, they've all awoken to the potential of supreme hegemony. Instead of all going independent, they are much as the successors of Alexander in OTL: they mostly want dominance of all Hellas for themselves, so they've started fighting each other.
Kyrenaika, still a republic, watches from the sidelines and prospers. As other philosophical schools are destroyed in the carnage of war (and Epikousos/Epicurus - the main competitor of the hedonists school of Kyrene - never even makes it big), Kyrenaika is an oasis of peace. A true "African Athens". The philosophical school of Aristippos gradually becomes very popular as the wars die down. With all surrounding regions severely weakened, and untouched Kyrene having become rich trading with all and fighting with none, the post-war era sees Kyrene as the political, economic and cultural focal point of the entire region. Their empire is one of trade, and it is never one of the greatest empires, but with everyone eager to put bitter warfare behind them, it is a wealthy, mercantile, tranquil empire... where hedonism is the cultural norm. There has been enough suffering in the last age... now it is time for the decades of pleasure and mirth!