IDEA for Solution to Wordpress Duplicate Content on Tag and Category pages

I have been thinking lately about how I use the All in One SEO plugin for wordpress. I know that some believe that duplicate content is a huuge deal. Even if it is not, I would prefer to have as little duplicate content as possible. At the same time, I obviously want to index as many pages as possible that contain relevant keywords.

Right now, I have been using noindex on my tag and archives pages to avoid duplicate content. I was thinking that I would like to index my tag pages as tags are essentially keywords that we would like to optimize for. I was thinking of a way to index the tag pages while still avoiding the duplicate content issue and I think I have an idea that may work.

IDEA: Have a plugin or a function that allows you to have random sized excerpts on different pages. For example, you could set an upper range and a lower range of number of characters or words that the excerpt should contain. Then, for each post on each page (mainly tag pages vs. category pages), the excerpt chooses a random number of words to display. This way, it should look like less duplicate content in google's eyes.

As I'm writing, I started to think that maybe its not a good idea for the pages to change each and every time so maybe you could just set tag pages to have say 75 word excerpts and the category pages have 125 word excerpts. That way, you have some consistency and the pages are not changing for every visitor.

I looked around for some plugins and I found a couple excerpt plugins but none that had this specific functionality. I wonder if such a thing exists or if this is even a valid idea. What do you guys think?

Excerpts on Home and category pages will alleviate the duplication of content problem.

But frankly I have never written two excerpt commands within the same site. Category pages are produced from "Archive" pages, that being said they will match the home page excerpt.

However, if you created custom category pages, theoretically you could do this by adding the excerpt counter to the base category query/the except/the length of the excerpt/ to accomplish this, but, IMHO, you are getting into the deep end of the pool.

so you dont think that the potential benefit, if any, warrants the trouble?

I was just thinking that if you have say, 1000 tags that are relevant search terms, it couldnt hurt to have those extra 1000 pages indexed. then again, who really knows about any of this stuff...theres no telling what is and isnt true.