Thanks. This is interesting, but perhaps incomplete.

I'd speculate that the location that you mention the PIE migrants encounter Soma as BMAC is incorrect. Soma has since been identified as the species Ephedra pachyclada that yields the stimulant Ephedrine. This particular species is geographically bound to the hills of Afghanistan. The identification was based not just on morphology, but also from the Parsis of Bombay, who had been continuously using Soma in their rituals, bringing it in the dried form from Afghanistan.

However, it is probably true to say that the migrating PIE pastoralists did borrow much from the BMAC, including linguistic innovations as well as mythological characters (for instance, Indra and Vishnu)