I think i suggested (probably in IRC) using the actual translation system for this. Translation files are editable (ok, maybe not thru the tiki interface) and you can translate tiki into english, so you can translate i.e. "Articles" as "News".
But this idea could go a bit forward, without requiring changing all templates. In templates, exist already a way to changing the bundled strings for others, and that is used by the translation system, as i said before. But if that is not enough, maybe another "layer" of translation could be used, something very like hotwords in administration, where on load of the current language.php (or in the translate function/tr modifier) you do a seach/replace of strings to your own way to see them. This could slow down Tiki a bit, adds another administrative option and another table, but enables you to do that changes db based (i.e. still works even after upgrading tiki) and not requires changing most templates.