I want to write a plugin which prevents wordpress from creating an archive page (I mean that the url must not exist) for a tag which is used only on an article.

This means I should modify:

• the query which returns the list of the tags for creating all the archive pages /tag/*
• the query of the sitemap
• [for the tags associated only to one article] the redirect from the old /tag/pinco.htm page to pinco.htm
• modify the template of those tags on posts to show them not like links but only like labels