I'm not sure how long you've been around, but before BPE came along, large vocabularies were actually quite a pain in the ass. You can find lots of literature around it before maybe 2016 (can't remember exact dates to look and I'm feeling lazy).

IIRC, a big issue was the final prediction layer. Say you're predicting a sequence 4k tokens long. Then you have 4k times vocab-size predictions. With a 50k token vocab, that's 200M predictions in memory (roughly 1 gig with floats). Lets say we want to equally compress 20x more languages, so we get 1M tokens (speaking super duper roughly), which means nearly 20GB just to represent the logits. If we wanted to handle a 40k long sequence, it's the difference between 20GB and 200GB of logits.

That said, BPE just takes in sequences of more-simple tokens. If you want to feed it unicode, go ahead. If you want to feed it something else, that will work too. It seems like you're mostly frustrated that LLM investments are focused on english right now, which is valid. Tech investments in general have a strong silicon valley bias, and a zillion people want to recreate that elsewhere. But that's a very hard economic question.