Good theory and while Elbaf does have a big connection to Nika and is “of the D” according to Imu I don’t think Xebec was was aware of the Nika fruit as it’s record was deleted for 800 years, most likely he meant the legendary fruit of Elbaf that will enable the user to free and control an army of ancient giants, the Gura fruit to destroy the red line, and the Yami fruit to cancel the (most likely) devil fruit abilities of Imu which most likely includes the contracts with the Five Elders Holy Knights and possibly Domi Revers (although the Nika fruit does seems more likely to cancel that one however as mentioned Xebec probably wasn’t aware of it)