YT...great posts, but I've got to jump in here and respond.  You asked, "Why guess a Jewish holiday for the rapture of the mostly Gentile Church?"  For the simple reason found in the following Scripture: "But if some of the branches (Jews) were broken off, and you (Gentiles), being a wild olive, were grafted in among them and became partaker with them of the rich root of the olive tree...." (Romans 11:17 NASB) 

 

Another thing that might help your understanding is this paragraph (pgs 6 & 7) taken from Edward Chumney's book THE SEVEN FESTIVALS OF THE MESSIAH:

• Traditionally, non-Jewish Bible believers understand the festivals to be exclusively Jewish feasts.  However, Leviticus 23:1-2, 4 tells us very clearly that these are festivals of the L-rd.  In reality, G-d in His divine wisdom instructed us that these festivals are for both Jew and non-Jew, and are to be celebrated jointly with each other (Deut 16:10-11, 14-16).  In Deuteronomy 16-11, 14, the word translated in English as "stranger" is the Hebrew word ger, which means the non-Jew (Bible-believing Gentile) who has joined himself to the Jewish people.  Therefore, the L-rd is the Host of the festivals and all Bible believers are His invited guests."

So continuing that thread...4 out of 7 feasts have already been fulfilled...3 remain (Feast of Trumpets, Atonement, and Tabernacles).   Some of the names, themes, and idioms for Feast of Trumpets, Rosh HaShanah, are as follows:

1. Teshuvah (repentance).
2. Rosh HaShanah (Head of the Year, Birthday of the World).
3. Yom Teruah (the Day of the Awakening Blast / Feast of Trumpets).
4. Yom HaDin (the Day of Judgment).
5. HaMelech (the Coronation of the Messiah).
6. Yom HaZikkaron (the Day of Remembrance or Memorial).
7. The time of Jacob's trouble.
8. The opening of the gates.
9. Kiddushin/Nesu'in (the wedding ceremony).
10. The resurrection of the dead (rapture, natzal).
11. The last trump (shofar).
12. Yom Hakeseh (the hidden day).