After playing the Ottoman Empire for 111 turns, I feel that the A.O.R. recruitment system is a little weak...
How bout an AOR Crimean unit? The region is 60% Islamic, therefore willing to take up the cause of the Ottoman Empire if taken from the Russians!
How bout making some exceptions to European units? The Hungairan Hussars, the Hussar original, is a regional unit unique to Hungary, usually one of the first counrties I invade. (This however, should be the only Hussar unit recruitable by the Ottomans.)
Prehaps the Swiss might be willing to fight for the infidels for a slightly elevated price?
Maybe add a camel unit at trade ports?
And prehaps you could make a new mission to take Moscow with the reward being Unicorn Technology. That would be certainly fun and intresting.
I also think religous unrest could be toned down a little more, I'm still noticing religous unrest as high as 7 in parts like Lithuania (maybe add another tech that futher reduces religous unrest?), and because of this, I tend to give the regions away to my protectorates, it's kinda ridiculous. Half of Austria is owned by my protectorate Italy, Half of Russia used to be a part of protectorate Courland before being sandwiched by Russia and Prussia, and my attempt at taking Moscow has left a trail terrorties I've given to protectorate Crimean Khanate, the only new terroratories I've been able to hold on to is just Kiev and that region north-east of Vienna. Prehaps you can grant the Goverment buildings of the Ottomans an extra repression bonus? Cause I can't keep these territories. In fact, it seems even on "normal" Prussia can afford a full army stack for every territory it owns thus giving it excellent happiness from garrison, while at best I can only have a third of that and must constantly juggle unrest.