There are rumors that George Kirk will return in some form in Star Trek 4.
Flashbacks seem to be the expected way, but…
Narada was originally a mining ship, but she was refit by the Tal Shiar with Borg technology. Unclear if it was reverse engineered designs or actual salvaged equipment, if the latter… Well, there’s some potential.
So the Tal’shiar installs salvaged Borg equipment on Narada. Not fully understanding how everything works, they don’t realize they are installing assimilation equipment along with the weapons or shield generators, or do and can’t figure out how to disentangle it from what they want to install. But they figure it’s not going to assimilate anyone without a command to do so, so what does it matter if it’s sitting there? Narada is a huge ship, they have the space.
Flash forward(backward?) to the battle with USS Kelvin. George Kirk crashes Kelvin into Narada. Now, this is assumed to kill him straight away, but perhaps he survives… albeit critically injured. The Borg equipment misinterprets the injured Kirk as a severely damaged drone, and emergency protocols activate to repair the drone.
George Kirk as the Kelvin timeline Locutus. Perhaps a few other drones from other critically wounded Kelvin crew and maybe a few Narada crew near the damaged sections.
It’s a path to bringing in the Borg to this timeline.
This could seem iffy right after another hive mind type of enemy- the Swarm from Beyond- but they could present that Swarm as a precursor to the Borg. I’ve had the thought that it could have been an early version of the Collective tech, and Altamid the homeworld of the original Borg. If they make this canon, and follow it up with a Borgified George Kirk, that could be pretty cool IMO and maybe even make Beyond the second best movie of the reboot. The experience against the Swarm might also open up ways the relatively less advanced Kelvin timeline Federation might stand a chance against a Borg invasion.
They’d need a clever way to get these drones off Narada rather than using it to assimilate the galaxy, but that shouldn’t be too hard. Perhaps the assimilation equipment isn’t complete, and their full array of defensive equipment isn’t available, so the Naradas crew would beat them silly? So they steal a shuttlecraft and go somewhere to contact the main Collective and gear up for an invasion.