What if instead of two ultimates which last 15mn each, SE make 1 ultimate which last 30mn
More difficult (equivalent of 2-3 usual ultimates)
More prestigious
Introducing "skill check" (imagine you have to do "tea", just after getting through Golden Bahamut)
As they have less work to do (30mn dragonsong ultimate < 15mn dragonsong ultimate + 15mn omega ultimate), they can also add better cutscenes/new design for bosses and arena/voice acting/etc