What was the language spoken in Meluhha?

OK. For the sake of argument, without conceding my own preferred
hypotheses, let us assume that Proto-Indo-Aryan arrived in the
Sarasvati-Sindhu valleys (Meluhha) circa 1400 BCE.

If the civilization sites are dated to between ca. 3500 to 1500 BCE,
what languages could have been spoken by the settlers in Lothal,
Surkotada, Dholavira, Kotdiji, Kalibangan, Rakhigarhi, Ropar? These
are settlements which seemed to have a way of communicating with one
another. There are also indications that some Meluhhan colonies were
established in Mesopotamia.

Can PIE/IE, Indo-Iranian, Indo-Aryan language studies provide some
leads in this regard?

Or, should we start with Zide rejecting Sanskrit as "completely
inadmissile on the grounds of chronological incongruity...and so is
immediately discredited." (Arlene R.K. Zide, 1979, A brief survey of
work to date on the Indus Script, in: Gregory L. Possehl, ed.,
Ancient Cities of the Indus, Durham, Carolina Academic Press).

Let us keep aside the script (and epigraphs)problem. Is there a way
to figure out all the possible languages of the region ensuring
chronological congruity?

Let us assume that Kenoyer is right when he says: "The origins of
the Indus urban society can be traced to the socio-economic
interaction systems and settlement patterns of the indigenous
village cultures of the alluvial plain and piedmont. More
importantly, the factors leading to this transformation appear to be
autochthonous and not derived from direct stimulus or diffusion from
West or Central Asia." (Kenoyer, J.M., 1991, Urban process in the
Indus traditon. A preliminary model from Harappa, in: Richard H.
Meadow ed., Harappan excavations 1986-1990, Madison, Wisconsin:
Prehistory, p. 11).

What guidance can linguistics provide in resolving this language
problem? What linguistic studies should be undertaken in relation to
the history of this alluvial plain and piedmont? Is it reasonable to
assume that the region was a linguistic area ca. 3500 - 1500 BCE?
[Say, with speakers of: Nahali, Burushaski, Proto-Indo-Aryan, Munda,
Dravidian dialects]?

People arriving (if at all) from Bactria-Margiana Archaeological
Complex (what language?) after 1400 BCE will be chronologically
incongruous, for the purpose of the language hunt starting from the
4th millennium BCE.

Regards.