Disclaimer: The inciting incident for the premise of this fic rests upon the concept of Percy Jackson and Artemis being in close proximity to each other while also being the closest two people to a blast powerful enough to send them through a dimensional rift during the Battle of Manhattan. Having read through the original series, it has become clear to me that significant changes need to happen in order for this to be possible. For reference, Artemis is only freed to engage in the ground conflict when Poseidon reinforces the Olympians and takes down Typhon. However, by the time this happens, Percy is already fighting Kronos in the throne room on Olympus after the titan has cast a magic barrier preventing entry to or exit from the Empire State Building.
Since the original arrangement obviously cannot work, this plotline takes place in an alternate universe with a few changes. One of the things that bugged me about the original sequence of events was that Kronos kept sending in his forces piecemeal. While I understand that this choice was most likely made in service of the narrative for a more entertaining and lengthened 3rd act, from a strategic standpoint Kronos sacrificed far too many allies attacking this way. The ocean forces went in alone and then instantly died to the river spirits. Kronos went in once with the minotaur and then hung back until his final engagement. Hyperion went in alone and got tree-ed. The pig (Clazmonian Sow) went in alone and got bodied. The drake went in alone and got skewered. Over and over, Kronos keeps sending everything one at a time.
So here is my proposed alternative strategy where Kronos actually tries. Rather than spreading his assault over multiple days, he attacks in two waves: one in the morning and one at night. To make both waves as powerful as possible, he delays his attack until Typhon arrives so that he can time his second push with the walking maelstrom. For our purposes, assume that his first wave contains all the previously mentioned goodies: the minotaur, the pig, the drake, and maybe ⅓ of the monsters at his disposal, all evenly spread out across the bridges. The monumental conditions are meant to severely weaken both the defenses and morale of the demigods. Because it takes forever to take down the drake (with Clarisse obviously dragging her heels), the demigods get maybe three hours between the first and second waves. Assume that Selina and Michael are already dead (if you just asked "Who?", then they weren't memorable enough for me to address). Because Kronos is looking to win, he doesn't bother with sending Prometheus and instead has Prometheus hold the sky while Atlas fights (since Atlas is more useful in battle).
Kronos's second wave consists of the remaining ⅔ of his monsters/demigods and every Titan he has at his disposal. Given the 2nd book series, we know Krios has to guard the titan home base and Iapetus is out of the running having lost his memories. On top of that, Oceanus is keeping Poseidon busy. So, Kronos has himself, Atlas, and Hyperion at his disposal. We can also give him Koios (aka Polus, take your pick) since he's the father of both Hecate and Leto, the former having sided with Kronos and the latter having a bone to pick with Hera (maybe with a lie from Kronos that Artemis and Apollo would be spared). Epimethius and Menoetius would side with their brother, Prometheus. Overall, that gives Kronos 5 titan generals for the second wave. (I've only been to New York once. It wasn't Manhattan and I'm too lazy to research details that ultimately don't matter to this story. Assume they take 5 of the 8 tunnels/bridges that Percy names with Kronos hanging back until one of the 5 generals has a distinct advantage for blowing through the defenses.)
In the 3 hour reprieve that Kronos uses to regroup and wait for Typhon, Percy goes up to Olympus, talks to Poseidon on the throne, then prepares for the last stand. When the 2nd wave hits, Percy initially wants to go for Atlas but is convinced to go stop Hyperion instead when Chiron, Nico, and Hades arrive with their reinforcements.