toki pona actually because it has so few words usually uses a system called "sitelen" which is like heiroglyphs or chinese glyphs, where each word has its own symbol and you can combine them
in English you should still spell voilà using diacritics English doesn't use, you're just inserting French text into English text so it's valid in that context
just 14 sounds with no variations, no 2 vowels are allowed to be grouped together in a word, all sounds are the same length, and all words have the stress on the 2nd syllable