Welcome to MobileRead.
To be honest for "only" a couple of thousand books I would suggest you just crack on and sort it out manually. You can use the Quality Check plugin to do some of those checks. The biggest problem you will have with trying to write something like this in a plugin is "if author is known" for instance - "known" according to who/what? Some website? Which may or may not be incomplete even if you could find something which had a massive list of authors on it, that presumably you are scraping data for. Which may or may not match due to all the subtle variations that can happen with author names, hyphenations, aliases etc.
In my opinion it is a non-starter as a plugin. Sorting out titles and authors for a few thousand books using a combination of extract ISBN, Quality Check and visual eyeballing will take a tiny fraction of the time that attempting to write a plugin for it would take, even if you could figure out a solution to the not inconsiderable other issues