I just noticed... there's another thing about the script which makes Dravidian the better choice -- some researchers have discerned an agglutinative structure in the script, and Dravidian is agglutinative. I think I've posted that somewhere on FR... let's see... nope, can't find it right now.
AncientScripts -- Indus Script
http://www.ancientscripts.com/indus.html
Ancient writing found in Turkmenistan
BBC | Tuesday, 15 May, 2001, 05:57 GMT 06:57 UK | staff
Posted on 11/01/2004 10:24:57 PM PST by SunkenCiv
http://www.freerepublic.com/focus/f-bloggers/1265930/posts
27 posted on 11/03/2004 10:33:06 PM PST by SunkenCiv
http://www.freerepublic.com/focus/f-bloggers/1265930/posts?page=27#27