There is much wrong with many of your assumptions and many of the assumptions on ME Christianity here on FR.
““Allah” is the Muslim name for God”
“Allah” is the standard Arabic term for God (Elohim in Hebrew and Elaha and Alah in Aramaic are cognates of Allah) probably used by the earliest Arab Christians in the First Century and currently used by the Christians of the ME.
Christian books using the term date to before Islam. The Aramaic work for God at the time of Christ was “Elaha,” a cognate of the same word. Ancient Christian tombs predating Islam were often inscribed with “Abd Allah” or “servant of God.”
“Then, later, when the Christian missionaries arrived, they used the word that the Malaysians gave them.”
Christian missionaries certainly used the word “Allah” . . . back when Europe was extremely pagan and many Christian missionaries were coming from the Arab speaking world (Islam did not yet exist and some Western Europeans were busy sacrificing infants).
“Better to voluntarily go back to the ancient Malay name for God”
That statement makes no sense to me at all. Better to define God the way that Holy Scripture, the Church and Holy Tradition defines God than worry about the sound one makes when praying.
This argument that the word “Allah” can’t be used because a group tried to change its definition is the epitome of semantics vs. substance. How you define God is what’s important (WHO you worship), the guttural umphing you make is not. To make it so is pharisaical at best.
Islams Allah is NOT the same God as that of Christianity...and that IS the bottom line...nor will it ever be.