Migrating 1 site in a multisite from a.com to b.com

I have a multisite install with about 150 active sites. I would like to be able to move/migrate blog id 12 from a.com/site (content and all) to a different multisite install on b.com/site. In theory this is straightforward, but I cannot get a one to one copy on a new host (was on a.com/site and is now b.com/site). The end result has lost plugin settings, and configuration options and sites that simply don't render the same on b.com/site as they did on a.com/site.

I have tried the Updraft premium, WordPress Importer and Multisite Clone Duplicator plugins. Both the Updraft and the MultiSite Clone Duplicator support groups say that their plugins cannot accomplish this behavior.

I have also tried writing my own script, but we have 8000 or 9000 tables in my schema which makes most DB operations very very slow. Additionally, parsing the serialized option data for URLs to switch is extraordinarily prone to error.

I am currently on 4.3.1 in production, but have verified that the behavior is the same on staging environments where the WP version is 4.7.2 and 4.7.3 respectively. None of the above methods produce measurably better results than the others.

Is there any reliable method to achieve this result?