I made a deck for a friend some time ago using Athreos as a commander, it has more of a "life tax" subtheme than yours, but you can check it out for
inspiration:
https://deckstats.net/decks/27018/1730516-athreos-blood-taxes-for-mam-os(Sorry for the long maybeboard, my brewing process is... exhaustive lol)
But anyways,
in my opinion, to make the best use out of Athreos the deck should make your opponents REALLY think if it is worth to let you return whatever creature you control that happens to die. For that purpose, a bunch of small deathtouch-esque creatures do a lot of work, also creatures with strong death triggers. I feel that your deck lacks this feature in particular, but your take on it may work great anyways, cause after all you probably will return your "innocent" creatures more.