For someone like me who doesn't always have a computer and is always on the go, an audio book or a fan made "Let's Read" would be more appropriate then putting voice acting IN GAME. In game voice acting would be a chore for any developer outside a cut scene and would make sense if it was automated, like the TGS reveal of the Apollo Justice game. (But this wasn't even done for a game, just a preview. Although it'd be nice if they handled more in-game cutscenese in the Ace Attorney series like this). From a technical aspect for in-game dialogue, not happening.
I have actually considered doing a "Let's Read" of Katawa Shoujo. I work professionally in the theatre business, so I know how hard it is first hand at casting THE RIGHT PERSON. Although it is different with stage presence and all, voice is something that is taken into high consideration when choosing an actor or actress. I think it's even harder for casting VA's because your working with the voice alone, so you must be a master when it comes to that quality of your acting. Ultimately though, the two people who get the say in who is used for the work are the Casting Director and The Director. Unfortunately in some cases, the artistic vision of a director will be drastically different from what people had envisioned. I FEEL, personally, this is selfish if them, trust me. I've seen shows fail because the "Artistic Vision" of a director conflicted with the actors' real abilities, leaving to really out of place characterization. What this project would require is spot on direction and a spot on cast. Hard to please across the board. (Seriously, people are expecting Andy Serkis' Gollum level interpretation of characters up in this game!)
Regarding Japanese characters speaking English, if you've seen the Code Geass dub, "WE'RE NOT ELEVENS WE'RE JAPANESE", enough said. For those who haven't, if I could find the actual video of the quote, you'd understand to. (In my opinion talking about Japanese things when you have a accent foreign from that environment sounds awkward, leaving it accent-less would be the option that would be drastically less awkward, albeit possibly out of place.)
HOWEVER, this was not a deal breaker for me when it came to that dub. I mean, there are specific reasons why the characters in that show would NOT have any japanese accents, considering the Britannian occupation, but I wasn't caring. I was hearing voices tell me a story with the right emotion and it made sense.
It would work for Lilly to sound controlled to the point it makes her speech noticeably proper, but not have to affect on her non-existent accent. From there, it's open to interpretation on how a character speaks. Romeo and Juliet takes place in Italy. I hear no Italian accents, and neither does Shizune.
(
It makes me want to have accent-less be an officially recognized accent since that seems to be used so often.)
Edit: TL;DR paragraph > This >
http://tvtropes.org/pmwiki/pmwiki.php/M ... eInAmerica
HOWEVER, There's another problem regarding my Code Geass example, that thankfully fan works can avoid, but in the off chance if this thing got popular enough, the professionally done anime can't. AT LEAST ONE of the VAs in the adaptation will sound the same in a different anime as they do in this one. Some VA just don't have any vocal differentiation, and that's a thing that grinds my gears with dubs. It's harder for me to distinguish voices with the Japanese version of something, unless it's one of the REALLY popular VAs, but I barely notice. It gets really weird after while if you can't forget that Ichigo Kurasaki is trying to liberate Japan at the same time he's being a whiny priest boy that can't pilot mechs well or being a really broken robot that's not Sentinel in Marvel Vs. Capcom 3.
In all, if this is done, well or not. We're ultimately faced with the same issue with the voices of characters in an interpretation of Katawa Shoujo that Hisao faces with Shizune's voice in her story arc. He longs to hear her real voice, being forced to imagine what it could sound like to the point where what she speaks has a voice in his head. The only time when he'll be able to hear her real voice in reality is when they're having sex, which none of us will ever have with the fictional cast of Katawa Shoujo.
Speaking of which, how would we even handle Shizune's [voice]? Very hard question indeed.
tl;dr lots of great possibilities. lots of potential problems.