After my previous comment, I thought I'd better go do some performance tests on my project and see what sort of impact loading a bunch more json text files would have on performance.
I load the dialogue into the game during the first load screen. As a base line, with a 10,000 word dialogue file created in DD, the overall load time is 15 hundredths of a second (I'm loading other stuff too in this time).
I made five more copies of my existing dialogue file and loaded them into separate json objects. This represents my estimated word count once the game is finished sans localization. The load time increased to 20 hundredths of a seconds.
I'm actually pretty surprised by how quick this was, so I thought I'd test it out with 20 copies of my json file - about 200,000 words of dialogue. The time increased to 34 hundredths of a second.
At this point I got bored of copying events and realised I could probably just do this in a loop if I wanted to go any further with it. But it looks like performance, at least in terms of loading files, shouldn't be a big deal.