I'm wondering when several people have applied all their idiosyncratic ideas of how a document should be formatted rudimentary all throughout the document, if there's an easy way to homogenize the styling of the document so you get a consistent look of the headings, subheadings and breadtext throughout the document.
Set up a number of basic styles to match the sections of your document (eg, heading, subheading, body, fancy1stPara, etc).
When you come across another editor's idiosyncrasies, select that section and replace whatever formatting has been added with your new style. This is only a couple of clicks per change (once the styles have been set up) and won't be too onerous, except on a document as long as a book.
To keep from having to do this again (and again) in future, distribute the styles you have set to other authors/editors in the organisation, and have it mandated that they are used in the creation of documents. This way you'll get consistency, not only throughout the document, but also throughout all documents produced by the organisation (which the marketing ppl say helps with the branding a lot).
I'd also be inclined to rip out the default styles that come with word that you don't use. Too many choices lead to the hodge-podge of styles in a document that is causing you grief. It might also pay to get input from the other authors as to why they like their styles and incorporate their preferences where this won't hurt the overall presentation.
If you mean apply a style and 'blending' what is already there to create a more organic feel then the answer is no this can't be done, the styles are designed to overwrite, not work with what exists.