How about the easiest to see and implement one... Party leader doesn't get to change things by themselves and it requires a vote from the party. Doesn't seem too hard to me. Realistically, yea they have to do some coding, but it's a necessity and a very simple solution. As the saying goes, "sometimes the best answer is the simplest."

As an example to make my point super clear, you have this party:

Douchebag McCuntface, Dude McAwesomeguy, Dudewho Playsagirl, and Random fourthGuy.

Douchebag McCuntface is party leader, he waits till the end of the dungeon while the boss is dying to change the loot rules to either super high gold or a lootmaster so he gets everything.

Under the current system he can do that and it's not against the games rules therefore he won't be punished by NCsoft.

My suggestion would make it so that when Douchebag McCuntface decided to change loot rules a window would pop up notifying everyone in the party and at least 3/4 people would have to select "yes" and possibly type in "Change" to change the loot rules (similarly to salvaging/using a purple). If less than 3/4 of the people said "yes" the rules would stay at the default bidding rules.

Something they should put with it as well, a timer so that loot rule switching couldn't take place within a certain amount of time after a vote had concluded (fail or pass) to prevent people from spamming it. They could also make it so that anyone in the party could propose a vote for loot rule changing just for QoL.

This would be a quick and simple solution to this problem, make everyone who isn't like "Douchebag McCuntface" happy and give NCsoft room to do other things with their time. Honestly it seems like the most efficient way to solve this issue and shouldn't really take that long to code in and test. It's just a simple vote system that tons of other games have, combined with a word prompt to make sure people take a second glance instead of just instantly hitting "yes" or "cancel" just to get rid of the window.

I don't think it'd take much time for anyone with a little common sense to see this is an effective solution to the problem and wouldn't take long to evaluate/test, yes they may wish to view alternatives, but off the top of my head I can't really think of anything more efficient short of the completely unrealistic goal of changing the ToS to ban this kind of loot rule switching and then having an NCsoft staff member watch every dungeon as it's happening and being a moderator of loot rule changes.