Tuvok was just a nice bonus.
Imagine if you have the hots for two people you can't have and then those two people end up together. A lesser person would feel like they were trolling her every time they walked past arm in arm but Janeway decided to take the higher ground and save them so they could be happy together and not be dead and crushed with depression. That way when they broke up she could snag at least one of them.
After they get back to Earth Captain Janeway finds a note secreted in her personal logs from the Admiral telling her to not fuck it up this time and to grab the first one that comes on the market again in reasonably good mental health (as in, NOT CHAK if he is dumped since both the books and Endgame show him to be a headcase). But if he dumps 7 she can swoop in.
See how generous I am, I'm getting more and more generous as I get older. She can have Chak, Kes is off my hate list.. I am just so nice now.