Lavos planned to evolve so he could devour himself along the way. He woulden't care about his past self, only about his present self! Lavos marks one third of the TD (At least), thus, he's still there. The TD IS Lavos, only by virtue Lavos' mind is the one in chrage of this merge. He planned it, and he dosen't care a past self. Only about a present self.
Evidence? No? Oh. The Time Devourer thing was a fluke, there's no other explaination. And the merged being, while containing Lavos, was probably a new consciousness. Afterall, why would Lavos just create better spawn in (his) ideal future if he's planning to just eat the universe?
Evidence? No? Oh.
He would not be a new consiouness, because the game STATES Schala and Lavos had seperate mindsets. If they WOULD have had a combined thinking, why, Schala would have the parasite's mind. The TD is no longer Lavos by race, by genes. Not by mind. Why else would he send Chronopolis back in time? So the Planet could send a weapon of it's own, a biological weapon, that has genes he can merge with.
If you can't understand it this way, let's play connect the dots:
This was done so that it
would serve as a counter-
balance against Chronopolis,
which Lavos pulled here.
Belthasar:
The one who connects with
the Frozen Flame, in effect,
links with Lavos itself.
The actual Dragon God
was consumed long ago,
in the distant past...
Integrated by the entity
known as Lavos in a time
on the other side of the
dimensional darkness.
It was FATE that used the power
of the Flame to seal up the
Dragon Gods.
Therefore: Lavos sent back Chronopolis. Chronopolis and Dinopolis war. Dinopolis loses. DG sealed by FF, and forms a link with Lavos along the way. DG devoured to the link.
If so, Lavos sent him back to have him devoured. Pretty smart action. Making a scheme so great that uses entire dimensions must mark great cunning and power.