Congrats on all of your hard work PowerPanda! This looks to be a lot of fun to try out FF6 in a new way. Adding new storylines and features sounds awesome. I wonder if your efforts might entice the community to add things that the GBA version has (Espers, dungeons, Bestiary, etc).
I've seen a lot of people talk about combining our projects and that does sound cool too. If it were done, was there a lot of text changes to Divergent Paths to the base translation or was it just the parts that expanded the story?
I was able to add Leviathan, Flood, and Graviga from the GBA version. Leviathan is not gained by battling him though. See my lore rant above. I had ideas for implementing Valor, but it's far more complicated than just adding a new spell.
The dungeons are no problem on an expanded rom, but the extra Espers and Enemies will require expanding the data tables to include them. I got around this in DivergentPaths by creating space elsewhere. For example, Leviathan is actually written in Raiden's spot, and Raiden is not in the game (I merged him with Odin). The 4 new enemies were created by combining other enemies together (Soldier/Grunt and Cadet/Templar were combined, as they are almost identical, and the invincible Guardian was removed from the game. This created space for 3, and the 4th was put in over the top of Czar Dragon).
For the items, I don't even know how you would accomplish it, as the item ID is currently a 1-byte identifier, allowing for a max of 255 items. More items means changing to a 2-byte identifier, which is a nightmare I don't want to consider.
For combining our scripts, it's not too hard. Notepad++ will allow you to compare 2 text files to find differences. So you use that function to just skip straight to the lines that need to change, and you keep running it until it finds no differences. You are more than welcome to do that and release it as an addendum to DivergentPaths. I had originally done it myself, just for the script, but I decided I didn't want to get into the endless battle that is which translation to use. I would leave that to someone else if they wanted to, and just stick with the original. Note that I am aware of at least 2 people right now who are planning to merge DivergentPaths with a retranslation. One is doing an original rewrite, and one is trying to put in the GBA script.