People Misuse the Spark'd Challenge

@SqueamishNerd, yes, that is a good point too! 💡 Many people don't read the rules or instructions for other aspects of their life, so this would be no different. 😉  But in the case of the 8 sorority members, there was nothing about a wedding and the clothing looked like school uniforms with everybody matching.  So at least in this case it wasn't like what you wanted to do, as it was never intended to have anything to do with a wedding. 😞 

There are 5 themes : Beach, Jungle, Spooky, Rustic, and Desert/Casino.  I entered one couple for each category.  I also entered a wedding party (Bride, Groom, 4 parents, and a ring bearer & flower girl who were also the siblings of the bride and groom).  I had made them for the slideshow that my Desert/Casino couple had and then didn't want to waste them.  I did try asking one of the Community Managers if this was OK, but it was the weekend right before the deadline, so they were mostly likely off for the weekend.  But for all the other entries I just made 2 people. 
But at least there was a clear couple getting married .  I'm confused as to why anyone would submit a lone Sim or a pet for a wedding challenge! 🤔😃

As for your poly relationship, besides that it wouldn't be legal in many countries, I don't think the challenge could accommodate that because you would have to get a Mod to be able to do that in the game, and the challenge can't allow Mods or CC because that wouldn't' be fair to the console users 😢 who can't use Mods or CC.