I remember reading somewhere that the Dragon God(s) was being manipulated/controlled by Lavos in an attempt to secure the Frozen Flame. According to Belthasar,
The actual Dragon God was consumed long ago ... Integrated by the entity known as Lavos ...
Whether the six remaining avatars were free willed or not the game does not explain. However, if they
were being influenced by Lavos, here are some examples to back up my point:
1) We know for a fact the Dragons Gods were themselves manipulating Serge and Lynx in an attempt to steal the Frozen Flame. Harle was created for this purpose.
2) According to theory, Harle was created from the basis of Schala, whom Lavos is integrated with. As such, Lavos may have had a hand in Harle's birth.
3) The Dragon God(s) harbors a deep hatred for humans, similar to Lavos. Its final form also shares an appearance to Lavos.
So suppose the Dragon God was not borrowing these details from Lavos, but instead Lavos was giving them to it? It would finally present a reasoning behind some unexplained motives of the Dragon God, as well as mean that Lavos played an active role in the events of Chrono Cross.