Category tree vs Category web

So I have a client who is asking for multiple parents for categories.

Now I know I could recode nop to do this Tho I suspect it's going to be somewhat difficult.

However I have the feeling that beside various practical issues this is just going to confuse the users.

Does anyone have any information/links about why this idea is not a good one?

My fear is that they will form the following relationships;

A => B => C => D => A

Any help appreciated.

The simplest way to achieve this is to duplicate the category name under different parents. You won't get a convoluted navigation that way but long term upkeep maybe an issue.

A simple example

Mens
  -Shoes
  -Shirts
Womens
  -Shoes
  -Shirts

Yes and in your example it makes very good sense as the products in each Shoes category would be different.

My clients want duplicate products in the duplicate categories.

Having thought on it I may implement related categories (similar to related products).

This will preserve the category tree structure and avoid complicating the category menu navigation. I can build a relatedCategory control and drop it on the category pages.