To be honest, I think what a lot of us want more than anything is to be able to play many of the games our sighted peers can. While this is not always completely possible, companies like Naughty Dog have shown us just what IS possible if a developer takes the time to work on accessibility from the outset. For me who does have a little sight, I would be happy enough with some more audio prompts in my games. I'd love to select a UI element and have the text of it read to me. I'd love to find an in-game document and have it spoken, even if just through text-to-speech. Otherwise I either have to read it visually really slowly, or use some OCR app on my phone. Either way it not only takes me out of the experience, but is also more time-consuming than it needs to be. I'd love to have audible qutime quick-time events as a selectable accessibility option. I'd love to have some sort of audio queue when there's an item or interactable object near my player character. It's these small quality of life impoovements which would make games more accessible. Because as much as I really hate to say it, audio games, rarely have the same narrative complexity or fun gameplay factors as the sighted world gets. Even if a developer can't make a game fully accessible, there's a ton they CAN do if they only had the inclanation and educated perspective.

BodachanS makes a good point in reminding that not all blind people are fully blind. So, what they refer to here is being able to properly zoom in and magnify things and still have things be legible and usable, I think.

Now as for fully blind people, it sort of depends on your platform of choice. On Windows, there are various ways to inject text directly into a screenreader as it were, which is generally preferred for people who use screen readers, because it gives the user the ability to customize the voice and speech rate for the game a lot easier than a OS-wide solution, which on Windows would be SAPI.

As for giving characters a particular accent, no, I'm afraid that's not all that easy to do unless you go with prerecorded speech of some variety, either voice acted or by using different TTS voices.

Depending on how many target groups you want to target though, working exclusively with prerecorded speech will exclude the deaf if there's not text to go with it.

As for UI, that is really hard to give you advice on given we have no idea what the game will actually do.

Like ...will there be mini-games to facilitate game interaction? WIll it be MUD-like in that there's a commandline that controls every aspect, or do you want a more button-press approach? Or a hybrid, MXP-like solution?

I can probably lend more useful advice if I know a bit more on what interaction patterns you are foreseeing.

Disclaimer; I'm a blind programmer currently working on a commercial MUD.

I second the idea that we just want regular games to be as accessible as possible. Use as much voiced dialog as possible. Make interface elements easier to read. Avoid bizarre fonts (Looking at you, Morrowind).

Most of this can be done without alienating sighted gamers.

Scalable UI and text, ability to make text and pop ups remain longer and be easier to read, ability to change font style. These are the ones I always like to see

Bigger text or the option to have voice speak. I'm only legally blind and have scleral lenses but my vision is still terrible and tiny texts makes my head hurt.

Edit to add: I love fallout but the color options for the pip boy/health bar is terrible. Better color options would be nice.

I can test the accessibility for you

I have achromatopsia.
If the game is an FPS, the color of the cross hair has to be changeable or I'll have a lot of trouble seeing it especially if it's red. Of course it goes without saying changeable size text is always nice.
And for extra points, text dictation as a lifesaver and improves the experience a lot. Even if I can read the text without it.

I'm sighted but work in accessibility, so take this with a grain of salt:
You'll want to allow full ability to change font size and color, background color, etc. Make sure nothing gets blurry if you zoom in too far. This is for VI people that aren't fully blind.
If you have voice acting, you'll want the ability to turn it off. Some people may prefer to hear the screen reader's voice, as they can set the speed, pitch, verbosity, etc.
You'll want to follow WCAG. This paste goes over it in quick detail for those new to accessibility:
https://pastebin.com/zy3KR7yL

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