I am creating a way of showing categories of "things" on a website.
e.g. i have a client who is a graphic designer and wants a page category showing all his logos and another page category showing all the letterheads he has created with that ability to add new categories in the future.

These logos and letterheads all have their own individual pages under their category page in the sitemap.

I have created attributes that relate to the logos and attributes that relate to the letter heads.

I have added the attributes that relate to the logos into an attribute set called "logo sorting options" and have added the attributes that relate to the letter heads into an attribute set called "letterhead sorting options"

I then tell the top level logos category page to loop through the child logo pages below it in the sitemap (using page list) and then query if they have attributes inside the logo sorting options set (foreach page list loop).

This then allows me to build out the category page like this preview:
http://mofo.co.uk.88-208-248-91.tseoc.co.uk/logos/...

I also do this for the other letterhead category page but i tell it to look at the letterheads attribute set.

My problem is that i have some attributes that only describe the letterheads or logos and other attributes that describe both logos and letterheads.

I would like to reuse attributes that match both sets but the only way i can think of to do this is to be able to add an attribute into more than one attribute set so that it shows for both categories.

attributes like color are very general and with the current set up i have been having to add a new color attribute every time we need a new top level category.

Does anyone have any thoughts on other ways i could achieve the same result?
Or perhaps concrete5.7 has some new ways of doing something like this?

Thanks.