Once you've got the translation fixed up, it'll all be about the presentation.
Please, please, please consider customizing the font a bit.
Lower-case descenders that appear completely above the baseline just make my eyes bleed!
OK, a quick look at the game (I'd never seen if before yesterday), shows that all the text is done as 8x8 background tiles, and not dynamically drawn into sprites.
That means no VWF, but, on the positive side, every piece of text, and box, that I've seen is spaced to allow for 16-pixel-high Kanji.
So once the game is 100% translated, and the Japanese font is no longer needed, it should be possible to modify both the font and the display code so that all of the english text is drawn as 2 8x8 tiles ... allowing for real descenders, and a slightly taller font, all without screwing up the overall look.
Since there's also the whole Kanji font bank in there that's permanently loaded as well, that space
could potentially be used to make custom bitmaps for some of the game's options, making those look even prettier.
Oh, and just for giggles, I checked, and it looks like there is a permanent "black" in the text palette, so it would be possible to add a drop-shadow to the text, even though it doesn't strictly
need one!
Finally ... there's a ton of unused space in the permanent gamecode banks (bank $00 and $01) to actually implement any code hacks.