I think it rather feels bland that you can not really change Turkey's stance in the war, which had fairly good interactions with Germany while still maintaining neutrality, it is known that Turkey had offensive preprations against USSR for in case Germany manages to take Stalingrad, which is not really unpredictable since Stalin would probably attack Turkey to found some kind of a Soviet Republic there if there were no that great power clashes, as those two countries were hostile too each other at that era (after 39)
There must be some kind of a neutrality mechanic like Switzerland and Netherlands that would be unlocked via the Kemalist Neutrality focus, and joining the factions focuses would require an amount of difference between influence tokens just like Netherlands', I mean high German influence should prevent the focus of joining Allies and vice versa. The power balance of the World War should also matter, as I said Germany gaining control over the Eastern front should increase the German influence whilst a succesful D-Day or Operation Red Dragon should greatly increase the Allies' influence and reduce German influence, which irl made Turkey to join the Allies at least on the page. And there could be some special decisions regarding the real meetings with Turkey: Adana Conference, where Britain accepted to lend-lease infantry and other equipments to Turkey to persuade them to join. The Turkish alliance focuses from each branch should also increase or decrease the power balance of influences and etc.
As a summary there were really great capabilities for Turkish Neutrality Mechanic to be made but I see that devs did not really strive for it even if there are precedents like Netherlands and Switzerland, I hope to see such a mechanic to be added with the War Effort patches free for all BftB owners, otherwise Turkey would just use its AI path that forcefully makes them join a side, always to the Allies if it is a historical game.