Glad to see interest in this kind of work re-ignite on Hive! I hope it will be successful! Maybe @howo can give you some pointers, he worked on something similar in the past on the previous chain (maybe even moved over to Hive, I don't recall). From what I remember, one of the biggest challenges of such a WP plugin, especially if you want to make it fully usable to the point of commenting and voting bidirectionally (both from Hive and from WP to reflect on the other side), would be that such a plugin would be quite heavy, and that's usually something WP website owners don't like, if they tweak for better SEO.