Okay. I'm going to level with you. I am definitely biased towards Cordelia. She's the one Peg Knight with the least ridiculous outfit and a good consolation prize for Say'ri not being an eligible bachelorette (Sully and Cherche are the only eligible G1 females that start in mainly physically oriented classes rather than specialty classes or magic users, but Sumia and Cordelia straddle the line with Peg Knight with Cordy hewing closer to the physical end of the spectrum versus Sumia's more magic bias).
Anywho, outside of the Avatar, Cordelia has the single best class set out of all G1 characters, hands down. Firstly, she starts as a Peg Knight which means she can either beeline it straight to Galeforce (and make it there before anybody but Sumia) or opt over to Falcon Knight to make use of her Strength (since her Magic growth kinda sucks, which presents her biggest flaw). Either way she'll get a lot of Speed and probably good Res too. Or she can head on over to either the Mercenary or Dark Mage classes for more solid base skills such as Armsthirft, Patience (+10 Hit/Avoid but only on enemy phase? When else am I going to really want that extra +10 Hit/Avoid?), Hex, Anathema (or I could just give myself an aura that nukes enemy Hit/Avoid/Dodge ratings that anybody can take advantage of). And then she also has Hero (for Sol shenanigans and Axebreaker I guess), Bow Knight (Bowbreaker on somebody who started as a Flier? Fuck Yeah!), Sorcerer (Vengeance shenanigans AND Tomebreaker? OH FUCK YES!!!), and Dark Knight (Slow Burn and Lifetaker? Eh, not the worst things I could take, but they have their uses.). Hell, even Lancefaire can get millage out of the Bride class if nothing else (plus Rally Speed and Movement aren't the worst rallies to have). Her only crappy skills are Refresh and Rally Skill (and even then Refresh is still kinda useful when she'll first get it).
That said, the three things that keeps her from being the single best character in the game is that a) she has a daughter with all the same classes and probably more (seriously, Severa's like the closest this game gets to a Ced or Larcei in that even with the worst possible pairing (which is Donnel followed by Libra) she'll still turn out solid as a rock) although she does have better availability over Severa, b) that her magic sucks (which makes combat in the Dark Mage line difficult at best unless she's seriously over leveled or you dump stat boosters into her, at least she gets Vengeance to help mitigate the issue but then you still need to both learn Vengeance and get your HP low enough to actually get some extra damage out of her; at least she'll have plenty of opportunities to raise her tome ranks in Dark Flier, Dark Knight, Dark Mage, and Sorcerer classes), and c) Morgan exists (and Morgan can do shit like maximize a stat like Strength, Skill, or Speed, get birthed by somebody like Aversa who passes down her Shadowgift skill to her where she can gain the fifty million skills of the game and the half a dozen magic using classes will all have access to Dark Magic, and so on and so forth).
In terms of main game performance you'll probably want her to stick with either Falcon Knight (for the superior growths) or Dark Flier (for Galeforce) then move on to either Dark Flier (if you went Falcon Knight) to make use of Lancefaire or Hero (if you went Dark Flier) for Sol shenanigans. I wouldn't go Sorcerer since her Magic growth sucks and there's not much she can do to mitigate it. She could go Peg Knight => Merc but Galeforce is the better skill over Armsthrift and she wouldn't get that much of a head start on Sol plus she'd have to go back to only an E rank in swords.
Edit: It would've been nice if you had actually made that post of your on the Cordelia's birthday rather than after it.