The generally accepted form of Dravidian root structure is (C)V(C). Here I am proposing a new form based on a word that identifies the fundamental unit of Dravidian population. Dravidian child.
In my variant of Malayalam (spoken in Kasaragod/Mangalore region) the word for child is, kDAvu. In standard Malayalam the word has become kiDAvu. Adding a vowel i in between or before the foreign words with CCV- root structure is a common feature of Dravidian speakers. eg. school -> iskUlu or prIti (Skt:love) -> pirIti (Kannada). This gives a good idea about the Proto-Dravidian form of Dravidian words.
The Proto-Dravidian words had a root structure of (C)(C)V(C).ie.
But it appears even before the downstream language families began to appear CCV and CCVC roots changed into CVCV and CVCVC respectively. As far as my knowledge goes, only one word has retained that PD form intact.