Y'know, while I'm not a super zealous "Liko NEEDS Armarouge to foil Amethio with Ceruledge" advocate, I was always a lowkey fan of the idea since day one. Nowadays I'm not quite as zealous about the idea but the more I think about it the more I actually like the idea even more than I did before for...a variety of reasons. It would fit her in a way that's both ironic and also not.
Namely yes, it would foil and mirror Amethio having Ceruledge but the foil would actually be in how ironic it is due to the two's fighting styles. Liko having Armarouge would be ironic for her, but it would parallel Amethio having Ceruledge which in hindsight is equally as ironic.
Armarouge: Believes in a fair fight, attacking head-on.
Liko: Isn't above being ruthless and underhanded, sly and tricky, being willing to use sneak attacks and surprise attacks and stop at nothing to win, including exploiting her allies and opponents alike to achieve victory.
Ceruledge: Willing to use sneak attacks and surprise attacks to win.
Amethio: Firmly believes in his sense of honor and abiding by principles of a fair fight, and will always attack head-on, he will never resort to underhanded means to win even if it would be more efficient.
There's another aspect of parallelism as to how it would parallel their influences by Diana and Hamber, two older adventurers who are longtime friends. Diana is Liko's grandmother and an influence on her, Hamber is Gibeon's family butler and Amethio's surrogate father figure and an influence on him. They shaped Liko and Amethio into who they are in many ways, even if Diana's way was more indirect with Liko compared to Hamber and Amethio.
I suspect if/when Liko gets Armarouge, the Fire-type will take priority, and if she were to Terastallize it, its Tera type will be Fire. Amethio's Ceruledge has Ghost as its Tera type, which means the Ghost-type takes priority, especially since it has two Ghost STABs in Shadow Claw and Phantom Force (Liko contrarily might have two Fire moves on Armarouge, presumably Armor Cannon and something else, and one Psychic move, maybe Expanding Force).
It would be a shoutout to how Diana's partner is an Arcanine, a Fire-type, and Hamber's partner is a Dusknoir, a Ghost-type.
The other side to the picture is Armarouge's signature move, Armor Cannon.
Above is the description of the move on the official SV website, where Armarouge forms a cannon and shoots its own armor out as a projectile that explodes on the target. In-game it's basically a Close Combat, at 120 Base Power and 100 Accuracy, but lowers Defense and Special Defense in exchange, which the description above also highlights.
In spite of Armarouge being intended as the more "noble" Charcadet evolution as opposed to Ceruledge being the more "ruthless" one (which is where it would be ironic for Liko and Amethio), Armor Cannon has a more ruthless and reckless aspect to it as well. Armarouge shoots its own armor as a flaming projectile, as a very powerful attack, but at the expense of its own defensive stats which highlights the reckless side.
It highlights Liko's more self-sacrificial tendencies and her tendency to put herself in harm's way to protect others (which is also highlighted by her Hattrem learning Healing Wish in Episode 94, a move in which Hattrem knocks itself out to heal an ally completely).
Armor Cannon in terms of flavor also has similarities to Meowscarada's Flower Trick in that it involves bombs/cannons and explosions. While Armor Cannon is more direct than Flower Trick (which involves illusions and trickery, toying with and deceiving the opponent), Flower Trick is basically flower bombs that explode, and Armor Cannon shoots armor as a flaming projectile that...explodes.
Explosions, blowing things up, recklessness, self-sacrifice, and aiming to achieve results at all costs...certainly reminds of someone, right?
(Coral and her signature "Glalie, use Self-Destruct". Heh, Liko and Coral are more alike than their polar opposite personalities would suggest. What are you hiding, Liko?)
Armarouge in general has a knight/warrior essence. While Liko isn't conventionally chivalrous and honorable like Amethio is, she still in her own way has the spirit of a knightly warrior. Because while she does have a more sneaky, underhanded, and ruthless fighting style, she has a compassionate heart where she cares deeply for people and Pokemon alike and is devoted to protecting others. It's something Grusha points out: Liko's true strength shines when she fights for others. That in itself gives her a knightly essence, even if she subverts the trope a bit by being guile and tricky, which contrasts the more fundamentally honest style of most of the non-Spinel Explorers, especially Amethio. Notably, this really shined when she faced Sidian in Terastal Debut, who is one of the more honorable and noble of the Explorers, who fights fair and has a Garganacl (Nacli was highlighted in that Charcadet episode as something that helped humans since ancient times), and prioritizes defending his allies over his own personal victory (something that contrasts and complements Coral who he's always paired with), and Liko's victory over him compelled him to share his name and not to forget it (which in Japan is a sign of respect, tying into knightly code of honor).
The above basically sums it up.
The last part is that Armarouge is part Psychic-type. While it would overlap a little with Hattrem, I feel as I said before that Armarouge's part Fire-type would take priority. But I do think Armarouge and Liko's Hattrem (and future Hatterene) would be a bit different, since Armarouge is more offensive and a warrior, while Hattrem is more support with Heal Pulse/Healing Wish with a bit of a devious side. Armarouge would likely channel psychic energy directly with Expanding Force, while Hattrem/Hatterene would use it more for healing or in offensive use, as a form of manipulation/using the opponent's strength against them, so there's still differences.
Nonetheless the overlap would be interesting because this would make Liko a Psychic-type user in a variety of ways. Which is honestly pretty nice to see that Ash's first successor gets to use a type he generally never had (Mimey being the exception but he didn't really use it until Journeys). Still, her use of Psychic-types also highlights how she has quite the battle intellect and is able to use her brain and perceptiveness to her advantage in battle. It also gives her a parallel to Chalce, who although has a closer rivalry with Dot as an intellectual, is also a Psychic-type user with Medicham and Xatu, and generally approaches battles with logic and strategy, and outplaying and predicting the opponent, something Liko is pretty good at herself.
I went on quite a ramble but I feel like there's a lot of ways Liko having an Armarouge would fit her, not just as a foil to Amethio but highlighting various aspects of her character. Incidentally, it would reinforce her as a foil not just to Amethio but various other Explorers members as well, especially Coral, Sidian, and Chalce. Which is interesting because all four were trained by Hamber, who is a friend of Liko's grandmother Diana (and even though they're not exactly on the best terms right now you can get the sense that in their younger days they were really close). Liko's narrative growth tends to be very strongly tied to the Explorers, not just the modern ones but the originals as well, especially since she's the descendant of Lucius and Rystal, and the Six Heroes and Pagogo awakened because of her specifically. Armarouge ties her pretty strongly to all of the non-Spinel modern ones especially post-timeskip, but it also highlights her character individually in several ways.
