You'll end out of space (on the NES rom). EarthBound Zero simply did not have as much text as the Tomato translation has.So I looked into hacking Mother 1/EarthBound Zero, and yes, as Schlupi said, the text system is really simple. But I can't just copy+paste the text, I need something that can repoint the offsets of all the text pointers because the lengths of the texts are different between EB0's script, and Mato's M1 script. This is my first time NES hacking, so excuse me if there are such tools available, but I can't find any. And I seriously doubt that Mato painstakingly repointed every single line of text in the game, according to his source, he has his own tool that finds the table and does the repointing for him. But that's for Mother 1+2, which is a GBA rom, not EarthBound Zero, which is a NES rom.
I remember reading somewhere that Mato said he expanded over dialogues and such as the original one had them cramped by size constraintes.
Also, if you want to avoid having to recalcuate LOADS of pointers, you're gonna need someone to program you a tool for that.