To reiterate a point I made earlier: Yes, Flint can do anything; he's as omnipotent as a man can be (at least against other humans). Indeed he could have had gallons of antitoxin ready to transport at the snap of a finger. Despite all this, he can't have the one thing he wants, to create an immortal lover for himself, one who is a separate independent person or offers the perfect illusion of one, even to her creator. Thus he holds out on Kirk et al
. to see whether their presence (or Kirk's, anyway) can enliven Rayna.
Really there are three tragedies that bring down the mighty Flint: the one in the past (having outlived every woman he ever loved, and presumably their children as well, although unmentioned), the one in the present (Rayna and her equally unsuccessful prototypes, a grand attempt to remedy tragedy #1 through sheer artistry), and the one in the future (his long-delayed aging and demise, the result of leaving Earth to stop repeating tragedy #1).
This is what makes Flint's (Akarin's) story worth telling; the special effects, and what they "really" represent, are all extraneous. (Although I'm glad the remastered version added a new exterior of Flint's base of operations. Wow!)