Anne's role (Maybe a playable Character? Why not?)

1) If she is to be a playable character, I'd like her to use all sorts of weapon types she normally has in her shop (basic versions, low grade) but be skilled with them, while not being OP. This until she would find more powerful ones.
Probably trained by Dominique in case of a (new?) monster invasion in the village.

As for magic powers, I don't want a Maria from Rondo of Blood 2.0.

2) Nah, she will be competent when it comes to managing the shop, especially if she made a promise to their parents before the latter died.
Willpower can really make miracles.

A different set of items? Discounts? I'm not too keen on this, unless you bring her special items she would need or items she lost and thought never seeing again.

3) Shopkeepers always need materials and other personal items. In sum, quests could fit, even if that concept has been overused (see answer 2).

And now for the killer question!
Playable? Maybe if she is not a bonus character, like Galamoth defined it (she would need a motive). But in the end, would you really want her to go against demons and Gebel and so on?

Maria's chances  in Rondo seemed to be minuscule, but she got the powers of the four cardinal beasts and has magic power. Is Anna made of the same mold? I am quite doubtful on it.

She'd better leave it to the professional demon-killers. She is perfect in a support role. Why send her to the battlefield?

A big issue in this game is the curse overtaking Miriam. In many stories like this, where the protagonist has a power they struggle with that could turn them evil, there is often one or more characters that really remind them of their humanity and keep them grounded - I think Anne is that character in this narrative. Anne to me seems like a humanizing character; a common person that Miriam can can connect with and help anchor her during her adventure. While its true that Anne and Maria (Rondo of Blood) were the same age, there is nothing in the material so far that suggests she has the ability to go toe to toe with various monsters and demons. I don't think she will be playable and her design is plain enough to also discourage that assessment.

With regards to the item shop, maybe Anne might be able to provide better access to more local items but I expect changes to the shop to be more influenced by where/when you are in the game rather than who is the shopkeeper at the time. Anne is described as a normally happy girl but the art we have for her is pretty morose. I would think, especially after that experience with her family, she would be a pretty mature girl for her age. I don't think there is any reason to dumb her down or infantilize her or make her too stupid to handle money.

For quest giving, yeah I see no reason you couldn't do that and I'd just make it work like it has in previous Castlevania games. I don't think you need to get fancy here or over-complicate things.

FUTURE DIRECTIONS:

So as I said, my expectations for Anne is as a humanizing NPC not a playable character. However, that doesn't mean things can't change in the future. A great point Saint Germain brought up is the passing similarity Anne bears to Sonia Belmont:



I could totally imagine, if Bloodstained takes off, Anne taking on the role of MC in Bloodstained 2 after some years have past, she's grown up and bulked up, and done some training. Some people are still a bit sore over what IGA did to Sonia (I've seen recent comments online from people who feel this way) and since Miriam is so closely associated with Swords, we don't really have a "whip girl". A grown up Anne taking on the role of a Sonia expy (similar to how Miriam is a Shanoa expy) in the future could be a nice, respectful nod to the fate of Sonia Belmont and I think make a lot of people in the community happy.

Using shop stocks (that are meant to be sold) on the battlefield is not only unethical, but broken too.
In that case, Anne would go "oh, I'll just gather max out all of the goods I can and go fight". Bloodstained is not a RPG parody.

Besides, if she were to be fighting, Dominique would be taking the shopkeeper's role. There is a business to maintain.
(of course the inverse is true as well)

I've always dug alchemist-type setups with bomb potions and so on, and try to use them(i.e. Diablo II exploding flasks), but every mmo/action rpg game I've played that toys with the idea doesn't do more than toy. They're never viable for late-game combat, only helping out early on. I'd love to come across a game where the idea is completely realized.

Sonia always reminded me of Doris, yeah. I don't see that much of it in Anne, though.

Her appearance and name are rather plain. My interpretation of the situation is that she will take the shop when Dominique's role becomes greater (to the point of playable). Much more is definitely a further leap than the other characters.

Oh, for sure, I think that may be while he has struggled for so long now with writing out the game's initial story - I imagine he realizes this is the start of an entire new mythos and wants to be able to lay out a long game of interconnectedness a bit better than Castlevania originally did. That would definitely be a wise way to go.

What little I know right now, I think I can say that it'd be damn awesome if Anne grew up to be analogous to Sonia/Doris, because I too felt that hole in the canon of there not being a female Belmont and it sounds great. I'm down if that's the case later on, but on topic from all we can see for Anne playable in present Bloodstained, I'm leaning no.

I don't see Anne being playable now, but maybe she serves an alternate purpose to the plot. Maybe she starts seeing a new purpose for preserving alchemy, since the events of the plot kicked off from that goal.