Slightly off-topic here, but also slightly not...

I love crusades (and jihads), and to me any game without them just doesn't feel complete; when I installed the XL mod recently, I played a brilliant campaign with the Scots but quit pretty much as soon as I realised that they too could not crusade...

Is it possible to mod the game so that currently-non-crusadable factions can crusade? I'd be interested in playing around with this, but having never really modded the game before any advice would be greatly appreciated!

I've heard that the issue is that these factions cannot produce crusade units (I presume this means things like the Crusade cross, Knights Templar, Order Foot Soldiers, Fanatics etc.) and in some cases possibly the Chapter House as well? (I know the Scots can build this in XL.) Would adding these units back in be sufficient, or are there likely to be other problems?

I also presume CA restriced crusades for a reason - could balance become an issue?

Finally (a challenge to differentiate the men from the boys), would it be possible to add any similar feature for Orthodox factions? Any ideas as to how that should/could work?