I know it's just your opinion, and I don't want this to be a long back and forth argument. I just find so much wrong with this analysis.
This is a very complex game, and practically everyone has yet to even scratch the surface. I still haven't even used some of the units.
I'm certainly no expert, but I think that at least one run of Conquest Lunatic can provide a somewhat informed opinion of unit usability.
The viability of units changes drastically from Hard to Lunatic. I made a post about fixed growths and this will strongly affect some units.
On Hard difficulty, every single unit performs well. Arthur, in particular, will benefit massively from his great growths on low difficulties. Even Nyx would perform well on Hard or lower.
Arthur ended as a level 15 Berserker on my Lunatic file. I kept him in the same class, because I didn't want to spend Gold on Sealing him. His performance was solid, but the Lunatic growths have screwed him up a bit.
I used Midori's Paralogue (without saving) to level him up, and check his level 20 stats. He has 54 HP (without HP +5), 39 STR, 36 SKL (capped), 27 SPD, 19 DEF, 8 RES. His MAG and LCK are both 0. His DEF and SPD are lower than usual, but this is still usable on Lunatic.
Units who performed well in Hard may not even be viable at all depending on how Lunatic growths treat you. This is why Corrin, Azura, Camilla, Elise, Leo, and Xander are the only true staple characters on any playthrough. Kaze and Niles may be staples just for their utility and mage/flier killing.
You can't afford to set aside multiple deployment slots for pure pair-up fodder, so your reasoning for giving Gunter, Charlotte, and Nyx very high ratings compared to potentially better combat units is kind of weak.
Mozu is bad for LTC players, but she can actually work on Lunatic! I actually made her an Archer and promoted to Sniper. She required too much babying, so I will ignore her in later playthroughs. But she does get good stats. My Mozu capped STR and SPD, though her defenses are slightly squishy. She was actually useful for some chapters.
Whenever I have time to do subsequent Lunatic runs, I will seriously attempt to use Laslow/Selena, Peri, Beruka, Benny, and Nyx because these are the units that I don't have experience with. I only used Charlotte on Hard, but have already witnessed her horrible performance as a high level Berserker. I won't even test Charlotte on Lunatic, since I now know that Arthur is much better despite his Luck. Nyx's atrocious early game performance turned me off from using her on Hard, but I never actually invested in her. It will be interesting to see if she ever redeems herself (on Lunatic, nonetheless!).
I have confidence that Beruka, Benny, Peri, and one of the Mercenaries (can't use both) will be able to perform their roles well. They obviously won't carry like Corrin and his siblings, but they will probably be able to contribute. I think Nyx will struggle, but I want to switch things up.