Too many hoops for my taste. Especially considering Abkhazia will be able to circumvent everyone of them apart from the prestige one, within a couple of years. And it didn't take a particularly prestigious Georgian ruler, to unify Abkhazia and Kartli. It took a simple inheritance.
936/955 Abkhazia would still need either Hereti or Klarjeti, which would take longer than a couple of years (for the AI) considering it would have no de-jure incentive to just conquer them.
By the time Bagrat III inherited Kartli and Tao-Klarjeti, he ruled Abkhazia for 30 years, successfully crushed multiple rebellions and received the honorary title for Kouropalates from ERE; I'd argue he had more than enough prestige. And while assembling the various titles was a matter of inheritance, declaring oneself King of All Georgian Lands - including the still independent Kakheti and Hereti - would definitely require a notable personality.
EDIT: Tao-Klarjeti and Kartli could be united as Iberia (
kartvelta samepo/Kingdom of Kartveli), requiring Klarjeti and Kartli; Georgia requirement could then be simplified to Iberia + another Georgian kingdom + prestige. With 936/955 Abkhazia holding 3/6 counties of Iberia (with the kingdom title held by Tao-Klarjeti rulers) and 2/4 counties of Kakheti-Hereti, special duchy requirements can be dropped, although I'd still advise them at least for Kakheti-Hereti (both for historical reasons and to prevent Abkhazia from quickly gaining it via Tiflis.)
(EDIT2: It might actually be 2/6 of Iberia, with Samtskhe under Tao-Klarjeti control as well.)
This method might not be optimal, but IMO a complicated-but-not-unhistorical solution is better than no solution whatsoever.