"Three five nine" is easier to say than "three hundred and fifty-nine", but the second option lets me have an order-of-magnitude number from the start. Take "one seven nine five four two zero eight three". Are you keeping track of how many digits you're hearing? "one hundred seventy nine million, <...don't need to pay attention to the rest...>".
But you did say "mostly". Are you thinking "one seven nine million, five four two thousands, zero eight three" or something like that?
If it were up to me, all the digit names would be one syllable, and the order of magnitude would get its own syllable (or a few, for very large/small numbers) up front. Basically a verbalization of scientific notation, but with the exponent leading.
This could be safely dropped for numbers of less than a few digits. "Two six" or "eight one four" is not going to be ambiguous/confusing.
No, not at all like Japanese. You’d have a single indication of the order of magnitude of the largest digit, up front, followed by a string of positional digits, where you just say the syllable for 0–9 for each place, including zeros.
The Japanese version is basically like other languages (including English), just with slightly fewer special-cased names.
Yes, instead of “one million and one” (5 syllables) it would be 8 syllables (or maybe 9).
On the other hand, 1,762,354 would be the same 8 syllables compared to 18 syllables in the current system (in English).
It’s possible some shortcuts could be added for several zeros in a row if that ever became useful. Or if the speaker were willing to break it up into the sum of two numbers this number could be expressed using 2 syllables for the 1e6 part, then the word “plus”, and another 1 syllable for the 1 part, so 4 syllables overall.
But you did say "mostly". Are you thinking "one seven nine million, five four two thousands, zero eight three" or something like that?