Dividing WordPress into Separate Sections

I am trying to figure out the best way to achieve a divided wordpress installation.

I want the wordpress to act as a knowledgebase but I also want to divide the content by areas that are specific to each section.

eg: Sales KB / Support KB

The problem is two-fold for me.

1: Each section I want to be as if it were completely independent of the other. I intended to use custom page themes to serve each section of the wordpress and with controlled post and category showing divide each area on its own.

2: I wanted to share some content so that it wasn’t necessary for me to republish the same thing for a separate area. However, I can’t for the life of me figure out how I would share content from “Sales KB” that can be pulled into the “Support KB” and still maintain the separate theme style using page themes.

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Would it be best if I were to just use WordPress MU and actually divide the sections into their own WordPress. Or is there a way to do this that I’m just not seeing.

Thanks