Salamun Alaikum,
There is no prescription in the Quran for any particular recitation during prayer. The Quran does not prescribe prayer in a particular language
[1], with any particular utterance or any particular form
[2]. The demand for the worshipper is that they know what they are saying (4:43) and to take part in congregational prayer
[3] with complete devotion. The Fateha is a beautiful prayer which has found common currency in the ritual prayer. However, the Pater Noster of the New Testament is also a beautiful prayer as is the Shema of Deuteronomy 6. The central point remains that the Quran prescribes no particular utterance for salat.
In a congregational prayer, it makes sense to have form for the purpose of communal adherence during salat. In private prayer one can arguably elaborate their prayers with other utterances which bring them closer to God and this would not be in contradiction of any Quranic verse. Ultimately, prayer is about personal spiritual communion, not a dogmatic ritual of utterances which leaves one spiritually unfulfilled.
[1] DO WE HAVE TO PRAY IN ARABIC?
http://quransmessage.com/articles/do%20we%20have%20to%20pray%20in%20arabic%20FM3.htm[2] HOW CAN WE LEARN PRAYER IF WE DON'T HAVE HADITH TO TEACH US?
http://quransmessage.com/articles/prayer%20without%20hadith%20FM3.htm[3] THE IMPORTANCE OF CONGREGATIONAL PRAYER
http://quransmessage.com/articles/congregational%20prayer%20FM3.htm[4] WHY DO WE HAVE TO RECITE THE QURAN BACK TO GOD IN PRAYER?
http://quransmessage.com/articles/recite%20quran%20back%20FM3.htmI hope this helps, God willing.
Regards,
Joseph.