Ah, everything I have ever felt regarding the Hogwarts Houses, stated concisely and with excellent metaphors! I feel like this line just about sums up every issue I've had with trying to sort characters into these four houses: "is this character's hard-workingness a reflection of their ambition, or do they only appear as ambitious because they're so hard-working?" There are also those characters whose ambitions are heroic in nature, and very few who are purely "smart/knowledge-seeking" without being ambitious or hardworking as well.

(also 100% British is a very good point! I've had people ask me to make a four house system for a Japanese school of magic which is...?? not a thing they would do?)

All in all, attempting to sort people, including good characters, into any classification system just irks my psychologist self. :p