Vixen and Mr. Terrific are phenomenal characters. They could work, but it wouldn't be my ideal pairing. Personality wise they could fit, but characterize I feel like they have different interests and day to days. Especially now that Michael is more super scientist and less of a business mogul.
I feel like they'd be of doing their own things. Michael would be in the lab or exploring, or investigating something. He'd be busy in 20 different projects. You know his work. Vixen would be at a fashion show, traveling the world. They would intersect with with work and at some events. But narratively I feel like one might limit the other. Unless you just fantastic four'd them and made them a family both doing their own things. And even then it might be limiting. I look at Reed Richards and Sue Storm and kind of feel like Sue should have married someone else.
That's why I felt like Vixen and John Stewart were a good fit personality wise. If John wasn't off in space so much that relationship would be more viable.
I'm not paying attention to this alleged Batwing romance. Didn't know about it and I'm just going to ignore the fact that you all brought it up. Vixen deserves to be with an A lister in stature and ability