It would be interesting to look at a 7/C story, just to see what the writer saw in those two. Compared to pairings like J/C, either Tom or Neelix/Kes, or even Tom/Harry if you don't mind a little bi-curious action, I just don't see the chemistry.
One of them is called "The Gift" and is an AU in which Chakotay is closer in age to Seven. The premise is that she's the sole survivor of a Borg cube that crashes on Dorvan V (Chakotay's home planet) and Chakotay's father, Kolopak, insists on nursing her back to health. Seven is about 15 in this story and Chakotay is a few years older.
Some of Seven's implants are removed (I don't recall exactly who did the surgery) so she looks more human; I guess it helps that in this story she's a teenager who doesn't have the extra 10 years or so that the TV-Seven does. She still looks noticeably Borg, though, and wears a hooded cloak when away from home so others won't notice she's Borg.
The people of Dorvan come to accept Seven, more or less, as Kolopak's adopted daughter and she and Chakotay have a sibling kind of relationship. She stays on Dorvan while Chakotay goes off to Starfleet Academy. She adopts a dog named Lucky.
When the Cardassians destroy the settlement on Dorvan, of course Chakotay joins the Maquis - and so does Seven. Fast-forward to "Caretaker"... and both Seven and Lucky are present on the Val Jean and when that ship is destroyed they both become part of the hybrid Starfleet/Maquis crew. Seven becomes Janeway's Science Officer.
Janeway is more antagonistic toward Seven in this story (the author doesn't like Janeway much and it shows - which is fine by me because I don't like Janeway either), but appoints her because her Borg knowledge is needed.
Kes remains on the ship as the Doctor's assistant. The story then becomes a retelling of some of the episodes of the series based on this AU situation where Seven has been on the ship from the start and her relationships among the crew are less stiff than on TV. Seven and B'Elanna are friendlier as well.
Lucky is allowed to stay on the ship (walks and presumably piddling take place on the holodeck) and the dog occasionally serves as a bit of emotional support for Naomi (she'll sometimes stop by Seven's quarters - she's not sent to live in Cargo Bay 2 - and ask to take Lucky for a walk).
It's a very long story that's still unfinished. The author has been working on it for many years. The relationship Seven and Chakotay have that began with him being reticent about accepting Seven into the household, to developing a sibling relationship that over the course of years eventually develops into them becoming a couple makes it a more believable pairing than the sudden "oops, there they are" of Voyager's last season.
This story is on fanfiction.net.
