The Undead, Elf and Dwarf councillors opinions are pretty clear and you can hear their opinions before you have to decide. The Lizards are almost certainly in favour because it increases personal freedoms, and the Imps don't really care about anything that isn't science related.
No, the game doesn't let you have any other choices. This is to force you to decide which of the options you prefer. YOU, the player, are the one who has to consider what she said. If you feel her arguments are weak and unconvincing, then side against her.
The game is not going to let you abolish marriage, seeing as you are required to get married as part of the storyline. I doubt the council would care much for that idea either.
