Add title calculation by a vocabulary string

I would like to write a module that is what taxonomy_title does but for a whole dictionary. My module should run before taxonomy_title - it would build the title by a string inserted for the vocabulary the term belongs to + the term itself. Only then, the taxonomy_title module should run and override specific terms if they have a specific title.

If I implement hook_taxonomy() and hook_preprocess() in both 2 different modules: 'a' and 'b' - which is overriding which?

Back to my question now; if I want my hook overrides to run before taxonomy_title ones, should I call it:
1. taxonomy_auto_title - alphabetically before taxonomy_title, or
2. taxonomy_vocabulary_title alphabetically after taxonomy_title.

Thanks.