While the bonuses granted by Islam are powerful and versatile, there is very little interactivity compared to the Christian world. It's all about managing a slider. To add some more interactivity, dynamics and immersion, I therefore suggest that it should be possible for a pious Muslim Empire to declare itself a caliphate.
The obvious problem is the already lopsided balance of the Muslim world, but I suggest this could be managed. First, the office should have the possibility to grant both benefits (relationship bonuses, claims, troop bonuses, tax, easier vassalisation of Muslim states, etc) and drawbacks (e.g. penalties for not being the most powerful Muslim nation, for bordering Muslim provinces of another sect, extra crusade penalties, obligations to intervene in wars, casus belli for infidels...). Third, historically the Mamluks would start off as the Caliphate, giving them the potential to compete with the Ottomans, although more likely they would slide into decline.
Interactivity could include:
Increased ability to intervene in wars between Muslims with penalties for refusal.
Casus belli on any province that converts from Islam to an Infidel religion (apostates).
Ability to "declare Jihad" under certain circumstances, with a functionality like that of a Crusade.
"Caliphal authority" slider (when low, this could potentially give maluses that could balance the Ottomans)
Claims on all Muslim lands once Islam is unified
And most important: ability of other , pious Muslim nations to interact with the Caliph for bonuses, similar to the Papacy.
Not all of this is entirely historical for this era, but there are a lot of opportunities and functionalities that aren't.
Thoughts?
The obvious problem is the already lopsided balance of the Muslim world, but I suggest this could be managed. First, the office should have the possibility to grant both benefits (relationship bonuses, claims, troop bonuses, tax, easier vassalisation of Muslim states, etc) and drawbacks (e.g. penalties for not being the most powerful Muslim nation, for bordering Muslim provinces of another sect, extra crusade penalties, obligations to intervene in wars, casus belli for infidels...). Third, historically the Mamluks would start off as the Caliphate, giving them the potential to compete with the Ottomans, although more likely they would slide into decline.
Interactivity could include:
Increased ability to intervene in wars between Muslims with penalties for refusal.
Casus belli on any province that converts from Islam to an Infidel religion (apostates).
Ability to "declare Jihad" under certain circumstances, with a functionality like that of a Crusade.
"Caliphal authority" slider (when low, this could potentially give maluses that could balance the Ottomans)
Claims on all Muslim lands once Islam is unified
And most important: ability of other , pious Muslim nations to interact with the Caliph for bonuses, similar to the Papacy.
Not all of this is entirely historical for this era, but there are a lot of opportunities and functionalities that aren't.
Thoughts?