Nice. My house was built in 1882 and as kids we used to alway find those antique glass, morphine containing, patent medicine style bottles... Didnt know at the time that everyone from the late 19th century/early 20th century was high as a kite. We used to just chuck em at each other.
I think basic yellow/browns are sweeter than whites. But you could also kick it up with some Walla Walla Sweets or Vidalias! More expensive, but if you only need 1-2 for a small batch, I'd go for it.
And since you are working with black raspberries, you could also consider purple/red onions. They tend to get grey colored when cooked, but if using in a dark colored sauce, they could work better than yellow onions.
Also consider Shallots. the flavor of both garlic and onion in one. Definitely caramelized.....!
Shallots. Duh. Now why didnt i think of that? Thanks for the brainstorm