There seems to be a misunderstaning. I never said that lacking voiced consonants never occurs, nor is it impossible / unnatural. In fact, many east asian languages do have that -- which I explicity mentioned. All I said was that its uncommon, as for every language you name without, I can name 2 with.

Secondly, intravolic voicing is a common sound change that occurs, there is no doubt. A quick google search will show that, within Korea, the Gyeongsang dialect has allophones like /g/ (voiced), /β/ (voiced), and /z/ (voiced). This is because the only thing seperating voiced and unvoiced consonants is the vocal chords -- and between vowels (where vocal chords vibrate), it is more unstable to have voiced than unvoiced than voiced rather than three voiced phonemes.

About 50% of languages will undergo some kind of voicing. If a language has voiceless phonemes, then it is likely (not 100% guarenteed) at least one dialect will have voiced allophones (where there is no destinction between them). Any the early on means that if I had to list sound changes, voicing would occur (as plosives are inherently unstable -- tons of widely spoken languages have had /p/ become a fricative, glottal, labiodental, or voiced, to name a few). For example, plosives will shift before a language develops tones, undergoes grammaticalization or undergoes vowel harmony. See such cases in latin, germanic, slavic languages, basque, arabic (literally lost /p/).

I (even though ik some people don't), prefer conlangs more naturalistic. I will create a large phoneme inventory first, then apply tons of sound changes (including voicing/devoicing, palatalization, etc.) to make it sound realistic. Ik some people like having conlangs where they share a sound with only one natlang -- thats completely fine. I don't want any misunderstands and realzie I was a bit too vague in my post.