Yeah, I think converting the manga to look like the VN's going to work much better.

Background images are a piece of cake to add to a scene, popping the characters in will be a breeze, and the script's super-easy to transcribe. Finding the background images and cutouts of all the characters are going to be the hardest part of all this (the latter of which was going to be the case no matter what)...probably take me longer to find them than it will to write up the script.

Worst case scenario on the backgrounds, I'll just have to go through the game and take snapshots while there's nothing on screen (thank you, space bar). Worst case scenario on the character images....well, without those we're farked. :[

Okay, quick update...

The dialogue from Chapter 1 of the manga has successfully been transcribed into VN format, and a quick test shows that it all works perfectly!

Digging up backgrounds and character images will take a little doing...I may have to go with Budgie's suggestion of simply cropping them from game screenshots myself. That's fine, since I plan on adding in a few details (namely Ryouta's necktie, Sakuya's scarf, and Yuuya's glasses/ahoge when those get dumped on him later) here and there anyway, to make them look a little more like their manga forms.

Also gonna need to grab a few more musical pieces and sound effects to round things out (thankfully I have all the sites Moa uses bookmarked now), but we're finally making progress!