If only these two characters actually met...
I really can't stop thinking about how an interaction between these two would have gone if they actually met, narratively speaking they fill that fatherly role, one raised Alicia and the other raised Maelle, despite being from different worlds and having very distinct personalities from one another, they both share that love to protect Alicia/Maelle, yeah Gustave would be incredibly torn about the whole "erasing the canvas" since Lumiere and it's habitants' future is what he swore to protect, but he would be the most understanding towards Renoir (besides Verso), that willingness to protect Alicia no matter the cost, that's something that the man who willingly gave his life in game for her would definitely understand.
I really think that Verso royally screwed up by being an ass and letting Gustave die, because not only I believe he would have been very vocally on his side with the whole "let's get Alicia out of the canvas, it's not worth your life", but probably would have helped everyone get a better conclusion, I do believe that he would have been that positive influence in Alicia's life that she definitely needed at the end of the game and would have been actually been able to convince her to get out of the canvas willingly (instead of the forceful way out in Verso's ending) and maybe, just maybe, said willingness to leave helps persuade Renoir to leave the canvas alone, since the whole reason to erase the canvas is because he doesn't trust his family in leaving it alone (especially when Alicia lied to his face about it), said route would also require convincing Aline in the outside world but with Alicia's help I could see it happening. I do admit that this whole scenario feels a bit fanficy, but when considering how much of an impact Gustave's death had in the whole party, just having him in the last act of the game to the bare minimum would have helped Alicia be in a better state of mind when making her decision.