I've started work on a newly acquired website app and am wanting to know the best path to deal with a large amount of keyword stuffed, duplicate content, landing pages.
This website is a webapp therefore the actual content the user is interacting with is dynamic and is hosted on a sub domain with robots.txt set to disallow all as well as noindex tags on all dynamic pages to make sure non of the dynamic content can be indexed or crawled.
In addition to the above the previous owner created 70 extra landing pages which are pretty much identical to the actual index page with just a few changes to stuff extra keywords (different meta information as well as single words that have been changed to the keyword he was trying to stuff in the content paragraphs for that page).
My main question is how should I deal with all of these extra landing pages which are all about 90% duplicate content and keyword stuffed. My goal is to remove them all together but I'm uncertain if I should redirect or flat out remove them and serve 404s or a mix of both.
I do not want to use canonical tags on the landing pages pointed to the index since they are really low quality and should be removed. I was thinking I should redirect some of the landing pages to one of the static pages which best suites the subject of that landing page while just 404ing some of the others.
In short, what is the best method to remove duplicate content, keyword stuffed, landing pages that were created for the sole purpose of attempting to gain SE traffic.
Just remove them and serve 404s? Redirect some of them to pages that best match the subject of the landing page? Redirect all of them to homepage?
My concerns are that of possible incoming links to some of those landing pages and user usability.
I'm pretty certain there are site wide panda/penguin issues so i know I have a long road ahead trying to fix this.