What do you think about Fatima bint Abdullah for Khalifa? Both are grandchildren of Saif by their mothers. Do you think Abdullah will let it done? What about Saif bin Khalifa bin Saif for her? Or Mohammed/Zayed bin Hazza is the most preferable one for her for being same bani Fatima?
Well, in Saif's male lineage there are three young good looking boys available: Saif bin Saeed bin Saif, Hamdan bin Saeed bin Saif and Saif bin Khalifa bin Saif, I see good chances for all three.
Khalifa has good chances with the daughters of Hamad bin Tahnoun and Mansour bin Tahnoun
Zayed bin Hazza is one of the options for Hessa bint Mohamed bin Hamad (she is definitely the most advantageous option for Hazza)
And we still have Zayed bin Mohamed bin Zayed, which for me is unpredictable, I can't even make a guess, there are several options with the same odds