If you and your partner have already decided you want to be together, could you perhaps get married sooner? Then you could apply for the reunification earlier, too. That is, if you have collected all the necessary paperwork.

In Switzerland, a religious marriage ceremony does not count as the legal marriage.
All couples have to go the to be married in the government office (in German: Zivilstandsamt) and are married from that date. For all formal purposes (visas, permits, finances, etc.) the date of marriage is that formal one.

If a couple wishes to hold a religious ritual, or a big party, they can do that afterwards, at a later date.