I have no idea whether Maronite Catholics were then allowed to retain Syrian or Aramaic. I certainly would not object and I think that it is a good thing to have Mass said in the Aramaic language used by Jesus Christ on Earth.
Two thousand years of history are a deterrant to posting the entire legacy. So, I'll begin with the 16th century and provide you with a link to the previous 1400 years ;-D
The Pontifical Mission of 1578
In the 15th and 16th centuries contacts between the Holy See and the Maronite patriarchs continued. Missionaries and papal legates continued to be sent to Lebanon. Often, they brought with them gifts of Roman altar vestments and furnishings. In the pontifical letters that were sent one can determine time and again the particular importance that the Popes attached to the adoption of certain rites and usages of the Latin Church, especially in the administration of the sacraments. And so the way was prepared for a systematic Latinizaton that would be accomplished in the succeeding centuries.
In 1578 Papal legates John Baptist Eliano, S.J. and Thomas Raggio, S.J. were sent to the Maronites. They brought with them a Papal Bull addressed to the Maronite Patriarch. After acknowledging the faith of the Maronites, Pope Gregory XIII requests that the Maronites should follow the Roman tradition in not adding references to Christ in the Trisagion, in having only Bishops administer the sacrament of Confirmation, and in not giving the Eucharist to children under the age of reason. The Holy Father closes by saying that he is going to send Arabic translations of the decrees and canons of the Council of Trent, and a catechism for use of pastors. We might note that the changes advocated by the Holy Father were of long standing liturgical practice in the Maronite tradition.
After meeting with the Maronite Patriarch, the Papal legates sought to examine the liturgical, canonical and theological books used by the Maronites. Father Eliano proceeded to censor and burn the books he considered contained errors. He has been accused by the Maronites of destroying many precious manuscripts important for the history of the nation. In fact, Patriarch Stephen Douaihi, noting that Arabic words often have many meanings difficult to understand, claims that Eliano was not a scholar in Arabic. Douaihi further observes that Eliano did not distinguish books accepted by the Maronites as contrasted to those of the Roman rite. On the other hand, Eliano's behavior is defended by the Jesuit scholar, Louis Cheiko.
Father Eliano had thought of building a seminary in Tripoli, but decided against it because of the persecutions and difficulties the Maronites suffered there. He decided that Rome was the only place. He asked that six students be sent to study in Rome, but only two were sent, Gabriel Adniti from Mount Lebanon, and Gaspar of Cyprus.
On his return to Rome, Father Eliano reported on the condition of the Maronites, praising their tradition and obedience to the Holy See and their joyful acceptance of the faith. Eliano told the Holy Father that, because some heretics were intermingled among the Maronites, some errors had infiltrated among them from foreign books and therefore the Maronites were employing improper customs. The Holy Father was happy with the report and thanked God for keeping the faith among a faraway people who knew neither the language nore the customs of Rome.
It would seem that Eliano reported on other Maronite practices that he considered objectionable and that should be surrendered. He stated that Maronites use both leavened and unleavened bread and add salt, that the deacons receive the Eucharist under both species, that the celebrant gives Communion to people from his own host, that there are no statues in their churches, and that they do not kneel in their churches. (We note that these are traditional practices among the Eastern churches.)
The Maronite position regarding the first visit of Papal legates Eliano and Raggio can be summarized best by citing the letter written by Patriarch Michael Ruzzi to Cardinal Caraffa, the Cardinal-Protector of the Maronites, dated August 25, 1678: "Since, my brother, there may be someone who will write to you that there are some words found in our books opposed to the holy Church, we accept only what the holy Church accepts, and whatever errors are found in some copies would have crept in and been inserted in them from the books of nations which are near us and from a long time ago. My brother, remove all suspicion concerning our rectitude; we were founded from antiquity in the faith of the Holy Apostolic Roman Church which we have always embraced; and we do not speak to you merely with our lips, but with our lips and hearts, may God be our witness."
Not related .. but thought you might enjoy this photo of Eastern Rite bishops. It was taken in April of this year, when they attended the Enthronement Ceremony of Bishop Gregory Mansour - St. Maron's Eparchy - Brooklyn NY.