I'm not sure what I'm having a harder time accepting about the Princess Knight - that she's 12 with that body, or that she wears her armor 24/7, including that terribly inconvenient-looking neck (?) guard.
Although it's pretty obviously set up with the maid as the only viable/inevitable choice (especially once her mysterious background is revealed to be that she has noble blood, since these stories in manga are always obsessed with lineage), in reality the obvious choice is the Princess Knight. She's the only one that actually helps the kingdom, politically, especially since the human royal family is on board with it. (Depending on how much power she actually has the witch could be a viable dark-horse candidate.)
Obviously that's overthinking things, though, since the story doesn't even bother to give any character a name. The fact that they are only roles/classes and not actual characters is the obvious tell that this is purely an exercise in shipbaiting. It was painfully obvious the Japanese fandom would go for the maid character, just like it was obvious that the gift choices were manipulated to get what the author wanted - the handy-dandy wildcard that the switch offers (Body swaps! Love spell! Hijinks!)
All that said, the parties for the village quest are obvious:
Fighters: Demon King, Brave, Priestess, Witch/Princess Knight
Healers: Villager, Maid, Witch/Princess Knight
PS: "Demon King" should probably be localized differently. Queen? Ruler? Overlord? "King" is not the right word to use since, you know, she's a lady.