The marquis may be saying it in jest, but I think he was only half-joking with his offer of allowing Elma to marry Snow. If it actually happens he becomes his son-in-law and not a mere stranger adventurer. Noble politics is all about making advantageous connections after all, and he praised Elma's strength. It would be 100% a political marriage though.
Luce, you gotta step up and act before any of that possibly becomes a reality.
The cat is finally out of the bag for Elma's noble lineage. Seeing Isabella's reaction to that after all her screeching about commoners was very nice, but they didn't show us Luce or Snow's reaction to that information. He might be disowned, but I can imagine the marquis would actually support him if Elma were to attempt to gain control over the Edvan house.