Making Puyol the marshal and Lucinda the chancellor probably would be having the most qualified people in those positions, but it would obviously also be extremely dangerous. It would make the Gijen family almost as powerful as the royal family itself.
I didn't even think of appointing Lucinda, but that seems like a really good ideal, to be honest. She's clearly ultra-capable, and Pujol would obviously like to have that sort of influence. But also, she's less likely to cause problems than he is, even if she's offered him her loyalty, and despite her results speaking for themselves, her being a woman would give just enough resistance to keep the good general on the defensive.
He's less likely to have a problem with it even if he gets snubbed for the position too.