One thing, though, is that you're using meta-ethics to mean ethics.

I'm not.

An ethic may say:
* I should support same-sex marriage. (SSM-YES)
or perhaps:
* I should oppose same-sex marraige (SSM-NO)

The reason for this position is the meta-ethic:
e.g.

• Because I should act to increase average utility. (UTIL-AVERAGE)
• Because I should act to increase total utility. (UTIL-TOTAL)
• Because I should act to increase total amount of freedom (FREEDOM-GOOD)
• Because I should act to increase average societal happiness. (SOCIETAL-HAPPYGOOD-AVERAGE)
• Because I should obey the will of our voters (DEMOCRACY-GOOD)
• Because I should do what God commands. (OBEY-GOD).

But some metaethical positions are invalid because of false assumptions (e.g. God's existence). Other positions may not be abstract enough that they could possibly become universal or apply to all situations. Some combinations of ethics and metaethics may be the result of other factual or reasoning mistakes (e.g. someone thinks SSM will harm society, but it ends up helping it, even by the person's own measuring).

So, NO, I don't speak necessarily about Collective Greatest Happiness Utilitarianism. I'm NOT talking about a specific metaethic, not even necessarily a consequentialistic metaethic (let alone a "Greatest happiness utilitarianism") I'm speaking about the hypothetical point in metaethical space that everyone would hypothetically prefer everyone to have - an Attractor of metaethical positions.