It seems to me as though the simple solution to this is to add a(nother) tarutaru NPC, in the place the Abyssea NPCs would have gone had there not been memory issues, that will warp you directly to the location of the Abyssea NPCs in Heaven's Tower.
You could even give him some cheesy text like "I know you adventurer-wenturers are so eager-weager to help-ey out-ey {first Abyssea NPC name I don't remember, possibly with Tarutaru accent distortion} and {second Abyssea NPC name I don't remember, possibly with Tarutaru accent distortion}, so I'll send you right to them if you wanty!"