I said it before in comments, but with Sonic X Shadow Generations having MEPHILES, the literal MIND OF SOLARIS, outright say he wants to REINTEGRATE HIMSELF INTO THE TIMELINE and EXIST?
Yeah, no, his whole plan in 06 was an ignorant self-destructive tantrum. Hands down.
His plan was to collapse time into nothingness; a void. The Time Eater erases time and space, rendering what it erases a void. Mephiles, Iblis, and Solaris are all inexistant in White Space.
Either Solaris would be POWERLESS after success and easy pickings for, say, the literal sentient all-consuming void at the beginning and end of existence since time - the literal source of his power - wouldn't exist anymore.
Or Solaris would be rendering himself inexistant through his own actions.
Both of which are VERY heavily implied in SXS.
He was doomed if he won and doomed if he lost.
Solaris is ultimately an expression of the futile and self-destructive nature of sadistic, nihilistic, and myopic sociopathy, and how even those who SHOULD be able to see how that ends DON'T and ensure their own demise.
Suns die, lights fade, space empties, time ends, reality becomes unreality, the finite depletes, the infinite abstracts, and All is Null and Void.
Gods are ultimately bound to their mythologies and scopes. No matter how much they try to claim and make it seem otherwise, they too WILL die and become nothing.
Inexistence is inescapable. To fight it is to delay it. It's better to make peace with it and live fully in the time that you have until THE END. Like Sonic.
Solaris was so focused on his sadistic rage, nihilistic vengeance, and myopic whims that he, THE GOD OF TIME, failed to do so and tried to EXPIDITE the end for his own pleasure. Not realizing until it was too late that he was playing himself more than anyone else.
As a result, everything is literally better off without him.
A dark and tragic fate, but one he literally asked for and worked towards.