A good personality is definitely the most important. Doesn't matter how pretty the outside is if the inside is ugly. Though that's true of everybody.
Succubi (and Incubi, for that matter) are kinda odd lore-wise in that regard, given they should probably be generically attractive enough for most people to not ask too many questions when they show up in your bedroom in the middle of the night going "hey stranger, wanna bang?" At the same time, they're still, y'know, demons, and being cast down from heaven and trapped in hell has got to say something about the type of "person" they are. I also like the idea of "biblically accurate angels" effectively being purpose-built for a given task rather than making biological sense. Like, a watcher angel probably would be a halo of eyeballs and a bunch of wings for a mode of transportation. If demons are fallen angels, and succubi/incubi are sex demons, then it kinda tracks that they'd be purpose-built for sex, personality included.
So that's what I tried to aim for. Nice to know it mostly worked out.
I really want to talk about it, but I really don't want to spoil anything about Arielle being the way she is, so aside from mentioning survivor's guilt (which is something that would've come out in a map event that is written and in the demo, but I didn't have time to make renders for it so it's locked up to not trigger), I'll try to keep it to things mentioned in the demo.
Baldric (the MC; I don't blame you for not remembering his name, you're able to change it pretty early on) is her hero. There's a line where Ynna says "You know she l-" and Arielle cuts her off (the implication being Ynna was about to out her romantic feelings), but Ynna was only going to say "looks up to you." He's quite literally her hero, and in the years she's known him, he actually lived up to expectations. It'd be like your favorite celebrity crush becoming your boss and learning that maybe they like you back. That's kind of an awkward position to be in (especially since most celebrities have their own love lives), but she also really wants to live up to his expectations of her the way he's done with her expectations of him.
Her literally falling behind due to low move (and you, acting through the MC, possibly making a deliberate choice to not leave her behind for the sake of the relationship system gaining points based on proximity) isn't a perfect ludo-narrative metaphor, but I thought it was still a pretty good one, and having someone in the party that can take a beating helps round the party out.
Ynna has a reason for not knowing any spells, too (ignoring the fact that the weapon she starts with isn't the weapon that gives characters the Charm spell), aside from the obvious "she was drafted" bit that comes out in conversation. You will eventually be able to teach her other spells as you find/buy weapons (which is another thing I think I want to rebalance a little; I need to do more testing, but I feel like it currently takes too long to learn weapon skills, and while I do want people to be deliberate about their choices instead of trying to get every character to learn every skill/spell, there are only going to be roughly 30 main story missions and I want people to have a good suite of skills/spells for that final mission, so I want to give out at least a few weapon options earlier than the end of the demo). Ynna's narrative on that front isn't nearly as complex or deep, though. It's like she tells you, she's built for something besides fighting.
But yeah, the differences between something like Fire Emblem compared to something like Final Fantasy Tactics is why I'm kinda torn on how to handle equipment options. I've played a large majority of Fire Emblem games, but I probably still have more cumulative hours in the different versions of FF:Tactics (that thing is my desert island game; I think I have two different saves from different runs over 1000 hours, and I've beaten the game at least a dozen times), so it's hard to say what the bigger inspiration is. I like the idea of giving the player that freedom, and I definitely want to experiment a bit with other entries (in what I'm really hoping will be an entire series because I loved making this demo) so I can try on a job system to see how it compares to what I've done here with the weapon skill system, compared to a skill equip system, compared to more traditional RPG "get skills when you level" system (though that's what my main project is, so I dunno that I'll do that for a strategy RPG).
I don't want to try to do more than one in the same game unless I land on something that feels like a genius idea, though. Implementing a skill tree might solve some problems, but it'd create a ton of work. And while I do intend to create optional side missions, I want to avoid implementing even the opportunity to grind. The idea that "players will optimize the fun out of a game" is something I've seen a lot of even before I decided to start making games, and it's a whole other thing seeing it up close.
Though there is something of a "specialization" aspect built into the weapon skill system. Each time you attack with a character, the game checks the weapon they're wielding and increases that character's associated weapon type skill (Sword, Spear, Whip, etc.). Then, it does some math and increases the specific weapon skill (Shortsword, Longsword, Greatsword, etc.) according to the type skill. Some characters have a higher weapon type cap, so later in the game, they'll learn weapon skills from certain types of weapons really quickly. They might also have lower (or higher) thresholds for preferred (or disliked) individual weapons, so it takes less (or more) work to learn that weapon's skill.
As an example, Arielle likes spears, but is awful with magic. Keep giving her spears, and it should be pretty easy to get her to learn all of the spear skills before the end of the game. Give her a spellbook, and it's going to take her ages to learn a spell to be able to cast it without the book, and it'll take a ton of work for her to learn all four spells and master that spell category. Getting her to master all spells in all spellbooks is probably impossible.
A change I'm debating making is giving characters a higher base score for weapon type skill, like Baldric starting with the equivalent of a C or B rank in swords, rather than everyone starting off with a D rank in everything. Possibly even going further and making C rank the default so you can see B rank is their preferred weapon type, and giving a character a D rank weapon might not be worth your time.
Though first I have to find a good way to display this information and get that implemented into the game, because I haven't found a plugin that does something similar yet, and I want to be able to show similar ranks for relationships so you have a base idea of relationship growth as well.
Spoiler alert on the "NPCs are just aspects of me" thing - same. I'm definitely not some smokeshow succubus that broke out of hell just to put lewds in games (disappointing, I know), so obviously none of my characters are exactly me. There's definitely some truth in the "write what you know" idea, but I don't see it as advice or a restriction, I see it as more of a fact of fiction. Regardless of what's being written or who is writing it, the writer needs some kind of frame of reference. When it comes to characters, sure, there's an element of "I like this idea for a character so I'm going to steal borrow it," but it's ultimately your brain writing, so there's going to be a little bit of you in there no matter how much you try and avoid it. I've been playing and running D&D and World of Darkness games for almost 20 years now, and have been writing homebrew campaigns for nearly as long, and my personal experience has been that you become more creative if you lean into that fact and leverage it rather than trying to write a character that specifically isn't you.
As an example to prove that point, there's a character in Maids & Masters that's nothing like me, so she's almost all trope. She's meant to be shallow, so it kinda works out, but I have a really hard time writing for her in some scenes. She's also basically the only character (in the harem, anyway) that I haven't heard anyone say they didn't either love or hate.