For starters, paring down the overgrown vowel system of Proto-rəgyam is a good idea for sound changes to start off with. In Proto-rəgyam it looks like this:
I am thinking of backing the central vowels into unrounded back vowels and losing phonemic vowel length, merging /æ ɛ æː/ as [ɛ], /ɛː e eː æi/ as [e], /i iː/ as [i], /ɑ ɑː/ as [ɑ], /ɔ o ɑu/ as [ɔ], /ɜ ɘ ɜː ɘː ɑɨ/ as [ʌ], /ɔː oː/ as [o], /ɨ ɨː/ as [ɯ], /u uː/ as [u]. Also, I intend on changing /æɨ æu/ to [eɯ eu] and /ɑi/ to [ʌi].Major Syllables
Monophthongs
The following monophthongs can be short:
front central back
close i ɨ ⟨iu⟩ u
close-mid e ⟨ei⟩ ɘ ⟨eu⟩ o ⟨ou⟩
open-mid ɛ ⟨e⟩ ɜ ⟨eo⟩ ɔ ⟨o⟩
open æ ⟨ae⟩ ɑ ⟨a⟩
or long:
front central back
close iː ⟨ii⟩ ɨː ⟨iiu⟩ uː ⟨uu⟩
close-mid eː ⟨eei⟩ ɘː ⟨eeu⟩ oː ⟨oou⟩
open-mid ɛː ⟨ee⟩ ɜː ⟨eeo⟩ ɔː ⟨oo⟩
open æː ⟨aae⟩ ɑː ⟨aa⟩
Diphthongs
All diphthongs are long:
front end central end back end
front start æi ⟨aei⟩ æɨ ⟨aeiu⟩ æu ⟨aeu⟩
back start ɑi ⟨ai⟩ ɑɨ ⟨aiu⟩ ɑu ⟨au⟩
Stressed Minor Syllables
front central back
close i ɨ ⟨iu⟩ u
open a
Unstressed Minor Syllables
front central back
near-close ɪ ⟨i⟩ ɨ ⟨iu⟩ ʊ ⟨u⟩
near-open ɐ ⟨a⟩
More will follow....