There are many scripting systems. Chinese-Japnese picture-based writing systems, Indian brahmi based syllabic system, Arabic writing system and then the Roman system used in English etc. Indian syllabic system is arguably documented very well with theory and all. Saraswati-Indus civilization in India had pictorial writing. Brahmi that emerged here, therefore, can be thought of as being an advancement over it. The Roman system relies on phonemes which the Indian system has already explored as documented by Panini in Ashtadhyayi. Syllable is an abstraction above phoneme. Therefore Indians landed on a system based on the syllable that most Indian languages use today.
The scripting created for First Nations peoples in Canada is based on the Indian Brahmi system. The missionaries who did it were by then clearly aware of the Indian system and therefore can not claim to have invented it. Rather they only adapted Brahmi to suit First Nations languages. This is my finding of a year ago. I will come back with more details on it. But putting details here for the record. I shared this information on Facebook in reply to this article (the article is confused, to say the least - but that is another matter):
http://www.huffingtonpost.in/2017/06/04/a-racist-tv-anchor-who-thinks-sanskrit-is-still-spoken-in-india_a_22124713/?utm_hp_ref=in-homepage&ncid=fcbklnkinhpmg00000001
Regards
Ragu Kattinakere