How to inherit the content of a parent node?

Hello,
Actually I don't know if I should post this as a support request or as a feature request... your answer could be a simple advice (a module, a snippet, a link, a way of thinking...). I am working on a multilingual website project dedicated to wallpapers. I defined two content types. Let's call them:
- "source image presentation",
- and "a wallpaper made from the source image".

The "source image presentation" content type could be seen as sort of parent of the "a wallpaper made from the source image" content type: for each source image presentation, one will always have many wallpapers available, so there will always be many wallpaper nodes. Each wallpaper node has a node reference to the source image node, and the whole thing is displayed with Views.

I'm using several vocabularies of many kinds (simple, hierachical, maybe a tree soon), in two langages, in order to help people finding wallpaper through a faceted search, with various criterias. Most of my vocabularies are common to both content types, thanks to the Content copy module. The faceted search will used to search among the wallpaper nodes only.

My will is to save a lot of time by making most of the wallpaper node taxonomies' fields inherit and store automatically the content of most of the source image taxonomies' fields, along with the fields' definitions (fields' formats).

The main idea is not only to display those inherited terms on a wallpaper node (Views could be helpful for that), but above all to attach them as metadata to each wallpaper node... and eventually, make those "children nodes" directly searchable with the faceted search.

Since a taxonomy term is a particular kind of content, with many forms (simple, hierachical...), I guess that this kind of function could be best offered at the widget level, but in a way I unfortunately ignore. I have thought about many solutions but always with PHP: using computed field, inherit taxononomy terms and put them as default content for each field... As a non coder, I feel that manipulating taxonomies through PHP is dangerous business. But I remain ready to create and test some (simple) PHP code, and make my vocabularies' structure more simple if needed.

So I am still wondering if you - or anyone - know a way to make this possible. Anyway, thanks a lot or providing, maintaining and improving such useful modules.