Forbidding hiatus between consecutive words is also quite valid.

Ancient Greek was against vowel hiatus rather strongly, especially the Attic dialect. I mention it only because it's rather amusing how many different ways it invented to eliminate hiatus: elision of the first vowel, elision of the second vowel, contraction into a long vowel or diphthong, epenthesis of /n/, epenthesis of /t/ (arguably, from -mn̥-).