These are my reasons I think Be'lanna and 7 make the perfect couple.
1. 7 of 9 being borg enhanced would be able to handle anything Be'lanna threw at her allowing Be'lanna to let go completely and not hold back.
2. Be'lanna is brilliant so is 7 of 9 they can have conversations that most of voyager would be hard presses to keep up with including Chakotay Janeway and Tom
3. Opposite often attract Be'lanna's passionate fire nicely complements 7's cool ice
4. Be'lanna has trust issues and feels inadequate 7 has no need of deceit and is extremely kind loyal and willing to sacrifice for the well being of those around her. All Be'lanna's fears would be unfounded with 7 and laid to rest
5. Both being halfbreeds can understand each other and what it really feels like to struggle with both
I have alot more but this is getting kinda long. What do you guys think?
Seven isn't a half-breed, she's fully human. And, I don't care if this is a popular point-of-view or not, but I think 400 years from now they will be able to cure most common genetic, epigenetic and developmental maladies.