Maybe I missed this from Petrosyan's paper, but the etymology of Argishti from the word argos meaning white, shiny needs also to explain the extra -ti at the end. Here an example below (Atreides) from Greek what it could be his function. Argishti which in most likelihood was pronounced as Argisti where the last -ti could mean descendance from a Argis. Basically the same as the Colchian name Argus.
If You look old Greek names the final -ti/te is frequent there.
So Argisti has a good etymology in Graeco-Phrygian type languages. The question is was this just similarity or we can really speak about the presence of an unknown Paleo-Balkanic tribe (not necessarily Greek ) in ancient Armenia. I think if we take into account words like burg-, udur, Rusa, then this presence become quite realistic.
The word Atreides refers to one of the sons of Atreus—Agamemnon and Menelaus. The plural form Atreidae or Atreidai refers to both sons collectively; in English, the form Atreides (the same form as the singular) is often used. This term is sometimes used for more distant descendants of Atreus.