Who is Phineas Vernon Welles?

Upon investigating the lore inside the colony ship, the Hope, you come across the very first audio logs of Phineas Welles. In these you discover he chose his own name.

This would probably mean Phineas Welles is a survivor of the crew of the Hope.
Digging through the rest of the lore on the ship, it is clear only two people could have survived. Either Phineas is the Chief Engineer, and cannibal, Frank, or he is the ships captain.

Is there any definitive proof as to who Phineas is?

Solution 1:

You can access his terminal after returning from the Hope, where he talks about his life before becoming what he is today. Added below is a screenshot of the log entry. For which you either need 100 hacking to reach, or you need to side with the board, in which case the door is busted open for you.

He was a board scientist. He became disillusioned with the board after they decided to sweep the Hope under the rug and went rogue from there.

Solution 2:

The logs indicate that Phineas is lying about his name, but they also indicate he was surprised when reviving a colonist failed due to liquefaction. Any crew member of the Hope would have been very familiar with that.

If I had to guess, I'd bet that they originally planned for Phineas to be a crew member of the Hope, but changed their minds at some point (Maybe that was simply too dark?) and decided not to explain his backstory- Maybe to be revealed in DLC or an expansion?