Guess what guys, this project is finished! v1.0 has been submitted to RHDN, but while we're waiting for it to be approved, you can get it early here:
https://www.mediafire.com/?mjhum130reilbdhPlease apply the patch to a clean Japanese Final Fantasy III ROM.
Note that if you find any typo's, PLEASE report them here in this thread. I tried to polish it up as much as I could but I also wanted to get this over with, so if there are any glaring typos or text-wrapping goofs, PLEASE report them in this thread and I'll have it fixed for the v1.1 release (hopefully there won't have to be a v1.1).
Unfortunately I was unable to implement a B-Button dash. Maybe that's something that could be included in a future release, but I had trouble getting it to work without disrupting the surrounding ASM code.
Oh and a quick question, will the text editing tool be able to edit the Japanese text in game? Also, if I edit the Japanese text, how will it turn out once an English patch is applied?
Yes it will, I'm gonna make my tool a bit more user-friendly before releasing it though, as right now it's tailored specifically to me. I'm not really sure how to answer your second question, you're only supposed to apply patches to the specific ROM file as indicated by the patch author, in this case a clean, unmodified, Japanese Final Fantasy III ROM.
EDIT: And the page is up!
http://www.romhacking.net/translations/2701/(I fudged up adding credits for Kea's MMC5 mapper patch but I've since submitted an edit to the credits list)