Absolutely agree on weakening the Ottomans
But on Constantinople: Why do you need a plague and crusade just before 1300?
In history, they only managed to occupy Istanbul in 1453, more than 15 decades later
Why do you want them to occupy right on spawn in the game?
This is needed, because that is one of the few setups that can make the AI conquer the city. I'm not talking about the human player, it doesn't matter how strong Turkey is, the human will conquer Constantinople. The AI won't, unless the setup I provided is present. At least a plague must be present, the Ottomans must be aiming for Constantinople (which is more likely in 1300), and if possible a crusade should seriously weaken the city even more. That is the way for the AI to conquer the city. If you have a screenshot of a Turkish Constantinople where this didn't happen, please share it with us.
Why weaken the Ottomans?? Since when have you EVER seen them penetrate Egypt/North Africa let alone take all of the Levant? I mean you NEVER see them take over large parts of the Balkans anyways, its a big disappointment, I say just weaken Constantinople
Yes, I have actually. Also, realize that any unit in the Balkans currently has no effect in Asia, because Constantinople is Byzantine and the AI doesn't ferry it's units effectively. If Constantinople is Turkish, that problem will be gone so there won't be a huge loss of power anyway.
IIRC, in the early Alpha stages we were trying to make the Turks more powerful, get them to capture Constantinople. At first they started around Ankara, but nothing happened. Now, they start on the west coast, 'which is unhistorical', but might also lead to a Turkey that conquers Constantinople. It doesn't so often (understatement, obviously

) however, so, to be clear, I'd say that upon the discovery of Flintlock (a tech that should be discovered around 1450), the defensive bonus of Constantinople should be removed. Walls, castles, the hill and rivers will do their job so even then it won't be clear.