Expanding on this I don't think I've ever seen a Grail War where Atomic Gatorade gets a Servant that is ruthless enough to work with him in-spite of the whole juicing children for prana deal. With Atomic Gatorade's wealth and connections he can supply Caster with resources enough to build a Golem army.
Since he has less prep-time, a lack of homonclus batteries and it's not an entire clan pouring everything they have into him this time around Caster's probably has a smaller lower grade quality force of Golems compared to canon. Still more than enough to be a real problem for the Fifth War Masters - Servants mind you.
I'm thinking that in a ironic end Atomic Gatorade gets thrown into Adam's core by Caster eventually. Given Gatorade's dog kicking personality Caster is probably less broken up about it than with Roche.
Further thoughts: if Illya does call up Mordred then she enjoys much the same position as canon by having one of the most powerful servants in the war. Compared to Berserker Fran and maybe Rider - Astolfo under Rin (if we decided to go with that) Mordred is going to a serious problem. Plus side for those opposing Team Saber Mordred can't resurrect like Herc and Shirou transformed into Siegfried can temporarily match her but still they are looking to be a major player.
For another Servant - Master matchup what if Assassin - Semiramis gets called up by Sakura? Since the way things have fallen out suggests to me that Kariya didn't save her in this continuity her situation should be some variation of canon and even if he did Semiramis aligns with a rescued Sakura on some points.
Semiramis would be an interesting partner for Sakura, she would flat out poison Shinji if the canon situation in the Matou household is in effect because and this is a direct qoute from her bio "she sees men who claim other women without a second thought as despicable." Also she's smart - invested enough to recognize that the Book of False Attendant deal would cripple her so yeah bye, bye Shinji.
Assassin is less passive than Rider personality wise. Rider in canon didn't kill Shinji because it would make Sakura sad and while unhappy with the situation didn't act until Sakura started going down the exact same path Medusa did. Semiramis seems likely to try and take Sakura under her wing and encourage her to take control of her life. Whether such efforts would blow up in everyone's faces and kick of a Heaven's Feel scenario or just result in something like Fate/hollow ataraxia Sakura is unclear to me.
Thoughts
@Omida @Ferian ?
Seems solid. Though, I have been thinking about the previous idea of connecting Fourth War with Apo servants with this one, with Sakura rescued and Semiramis summoned by Atomic.
So, we don't know how long it takes to be in Grandpa Zouken's Happy Fun Time Dungeon (TM) to turn person into Matou, but let's say that when Kariya and Waver break Sakura out, she is enough of Matou, that ten years later Grail picks her as Matou representative. So she goes to Fuyuki, to finally confront her past and free herself of it. She summons Spartacus, who will help her get out from under the oppression of her past
.
Meanwhile, Atomic Gatorade and Semiramis get along pretty well actually. The thing to remember is that Atomic discarded Medea as useless because he summoned her with the expectations she could summon Colchis dragon. Only when she says that she doesn't know how, does he turns into Asshole McDick. But Semiramis? If Gatorade summons her for her Flying Gardens, she can totally deliver on that. Sure, she needs shitton of exotic materials, but Atrum is wealthy enough, and sunk enough money into this already that he easily supplies her with needed stuff. And since he summoned Semiramis explicitly for her power, she can respect him just enough. She won't deride him for his magecraft, since her specialty is in poisons and all the big feats of magic we see from her are due to Flying Gardens, so she probably would just applaud him for finding a workaround to his weaknesses.
Meanwhile, Rin summon Rider just like her dad, if not such a powerhouse as Achilles. I am not cruel enough to inflict Astolfo on her, so let's go with another discarded idea from Apocrypha. Saint George. The guy dropped fro the script because in a war with Siegfried, Achilles and Karna in,
he was the unkillable one. So now, on the other end of the world from Europe, he doesn't get his ridiculous fame bonuses. He is still good defensive Servant, and since Rin tends to hang around the frontline and provide support, he meshes well tactics wise. He also tends to be goofy when off duty.
Shirou and Fran have their arc, Ilya and Mordred are either purely antagonistic force, or with Mordred forcing her master to give this whole sibling thing a chance.
That leaves us with Caster, Archer and Lancer. We have Zouken, who have been skulking around since Atalante and Kintoki fried his house and worm pit, we may potentially have Kirei surviving his encounter with Shakespeare, we have Bazett, who lost her Cu-summoning catalyst for the sake of the plot
.
No matter what though, if we get Avicebron in, and he gets his golem core, the 'good team' (Rin, Sakura, Shirou, with Ilya being solid maybe) have not only kaiju battle against Adam, but later on will have to assault Flying Gardens. Which is... less then optimal, given that there is no one in this war that has either the resistance or the cure for Semiramis' super poison.
...
Victory to Atrum Galiasta and Semiramis! Enjoy Angry Mango's birth
.