Grimoire is needed, because they have the protomateria to set up. Gast can't know about that, because if he does her thesis has concrete proof, and she doesn't get ostracised for it.
Genuine question because I don’t remember all the lore details, was he really needed? Like, couldn’t she just research it all by herself, and have everyone else be all “Lucrecia, would you be a darling and put that inconclusive nonsense on hold to focus on this beautiful Ancient specimen that we just found?”
My problem with Grimoire is that he’s Vincent’s father, and the only reason he’s Vincent’s father is that they wanted to give her a clear reason to reject Vincent that had nothing to do with Vincent himself, God forbid anyone thought that maybe she just wasn’t that much into him or that she preferred Hojo for her own reasons.
But why go through the trouble of creating the father of one of the most mysterious characters from the original game, and then making him so important for said character’s love interest, if you’re not even going to give me one scene of them interacting at all? What was their relationship like? What did Vincent think of his father? What did his father think of him? He died when Vincent was an adult, so he must have had an impact on his formative years. If he didn’t, why not? What about Vincent's mother? They worked at the same company (I assume)! Did his father get him the job?
That’s a lot of questions that I would have never felt the need to raise before Dirge of Cerberus. A lot of questions that the game doesn’t bother to address even remotely because then again, Grimoire is not really a character, is he? He’s just there to provide a plot point for DoC and make the relationship between Lucrecia and Vincent melodramatically impossible.
Also, I don’t fault Lucrecia for marrying Hojo, especially over Vincent (I don’t find Vincent such a better candidate to be honest
). I kind of pity her for that actually. Bad marriages with bad people happen in real life too, though it would have been great to see what she really thought of Hojo and if that changed over the years.
But I do fault her for willingly experimenting on her body and her unborn child in the name of science; that was on her too, and it was on Gast too, it wasn’t all Hojo. And I fault DoC for not showing us all the different characters’ opinions and feelings on the most important thing that happened in Nibelheim during those years, the Jenova project. For not showing us how the idea developed, how they all reacted to it. Maybe Lucrecia wanted to do it because she felt she might have been more listened to as a scientist, or maybe she did it because she truly believed in the project, or maybe she did it because Hojo manipulated her. Who knows?
You might argue that it was not DoC’s responsibility, since it had to focus on its own plot, but I don’t quite agree. The main character in the game is Vincent, and the Jenova project is the reason why he confronted Hojo and needed Chaos to survive, the reason why he slept in a coffin for decades to atone, the reason why Lucrecia tried to commit suicide and then decided to confine herself in a crystal prison forever. That project
defined them. And since the original game left it all in the air, DoC was the perfect chance to really go there.