Thoughts since I randomly mentioned Harry x Ivy on the Discord chat last night. Assuming the romantic part can take off, from a viewpoint of overlapping interests, it also works extremely good. Ivy eventually has to have a kid to keep the Archive lineage on-going. If she's worried at all about people kidnapping her kid, well, having a father who's committed genocide against an entire magical race for kidnapping his first kid isn't a bad idea. Conversely, there's a lot of lines she normally cannot cross a a neutral party to the Accords. But if people start targeting her or her hypothetical kid once she's a little more connected to Harry, that gives Ivy free ground to go loose on them.
Also, I think the Archive is supposed to be a witch, or at least a sorceress? It gets a little muddled in all the lore. But Ivy has used a significant and strong amount of magic on at least two occasions, once while she was still a pre-teen, well before most human wizards even start getting any magic juju. So having a daughter with Harry would give the new Archive-to-be some stronger magical heritage.