Its very difficult. Lebanon show how small multi-ethnic state could collapse. I think a "core" culture that gain control of state is probably inevitable on such small states (like Alawis on Syria or Sunnis on Iraq). retaining multi-ethnic nature of state would be difficult, especially with link between minority and neighbours. Also moder educational system is rather good on pushing "national culture".
Lebanon is an interesting case because it was created by the French to give the Maronites outsized power and influence in the region and resulted in inflammation of ethnic tensions and conflict within the state but then over time through shared struggle the Lebanese actually gained a coherent and unified national identity.
Even in the past decade or so where Lebanon is going through an especially rough patch and in many ways can be considered a bunch of statelets pretending to be a state, there’s still the idea of Lebanon that all the ethnic cliques hold to. I wouldn’t call Lebanon a win by any means but honestly I kinda admire the progress Lebanon has made towards coexistence even with its myriad of issues.
I don’t think any Middle Eastern state is a good example of a neutral ethnically diverse state being created since it was created with inherently non-equitable ambitions. Though saying that, any “Rumelia” that exists as an independent state will almost certainly be created with similar ethnic imbalances to serve a geopolitical purpose. So perhaps lebanon would share some resemblance after all.
Minor thing, Lebanon is multi religious not multi ethnic .
The distinction is semi-arbitrary. This is like saying Yugoslavia was multi-religious and not multi-ethnic. The ethnogenesis of these groups is influenced by religion. Both directly as religious/communitarian identity serve as the basis for the national identity and indirectly as religion meant these communities had divergences in how they were treated historically.
