That's still simply transliteration into the Roman alphabet, not Anglicization. Indeed no other standard national script currently uses ə, and even Azerbaijani texts sometimes use ä to conform with other Turkic forms of the Latin Alphabet. It's proposed for use in an Adyghe Latin script (ABX) in Turkey, and is used in Abenaki, which in 2012 had just 15 speakers. Some texts in Kinaray-a used it, but the orthography recommended by the Filipino Language Commission uses ë instead and for a different phoneme. So no you can't call it Anglicisation.