So over the last few days, I got the urge to hack BSFE a bunch. Presenting…
a bunch of unused dialogue! Offsets of text are also provided.
Episode 1:

0x7190E

0x71933

0x719AC
Episode 2:

0x719AD. Minerva’s line comes first.

0x71B03
Episode 3:

0x718A9

0x7194C. Ricardo’s line comes first in both instances.

0x71A4C
Episode 4 does not have any unused dialogue.
All episodes, however, retain every single piece of menu text in the vanilla FE3 rom. Every character name, every item name, every class name, the battle prep menu, chapter names, shop data, and even some debug menu strings! (Not that I know how to enter in FE3, let alone BSFE…) Their locations vary slightly between the episodes and it’ll take a while to figure out what goes completely unused in every single BSFE chapter.
In addition, there’s dummy text in empty text slots; this has been documented above. All pointers outside of the few lines required for a BSFE chapter (at the top of the dialogue pointer table) and the character death quotes (using the original pointer if the character was in FE3) point to the dummy string instead. Over five hundred pointers are dummied out in each rom.