Slitherine

In the pre-expansion map, the missions of reducing the Seljuks to three regions and removing them from the map entirely were difficult, but feasible. In the expanded map, however, they are essentially impossible, especially considering that the Seljuks often expand far into Central Asia and Siberia.

To replace them, I suggest these three missions:

1) Reclaim the birthplace of Christ - Own the region of Jerusalem and at least six regions in the Levant (domains of Filastin, Aleppo, Damascus)

2) Revenge on the Caliphate - Own the region of Baghdad and the entirety (?) of the domain of Iraq

3) Surpass Trajan - Own the entirety of the domains of Khuzestan and Sawad

I will try to pull this off with Estonia on Suicidal difficulty in my AAR. I report on how this goes. See if thats true. From what I remember you can rush them with Byzantines easily due to owning superior Heavy Cav and Heavy Infantry combined with Abandon action.

Good remark on the anti-Seljuqs missions.
I'm not against improving the Byzantium ones overall, but I lack time.

In my campaign as byzantine they declared war on me around turn 100 and it was fun to conquer all their regions but I did not have intention to keep conquered regions so i gave them to other factions because I wanted to expand toward west.
Played on very hard but it was little problematic to protect all conquered regions because they did have many armies and civil war did happen often during conquest so I was forced to have big armies and not to split and they did have many smaller and few big armies so after conquering region and moving to next they often tried to take it back.
I did not try expanded map but I guess it would be harder.

There are many more regions to the east ...