A liberal, on the other hand, will have a (well-meaning) vision for how a Great Society should be, and think about what actions government policy should take in order to cause that vision to become reality.
I think it's a little more complicated than that. When one person's decisions affect everyone else, what then? Is it liberal or conservative to try to control greenhouse gases, carcinogenic and toxic waste in the water table, deforestation, overpopulation, etc? I guess that wanting to control those things qualifies as a vision of a Great Society (or at least a marginally sustainable one)--and at least the late behaviour of the two parties is pretty consistent with your description. But if that's true, then the conservative platform is literally the platform of doom.
A liberal will say, "I think we all share a vision of what marriage should be, and the polls even in 2009 bear that out. Government should enact policies enforce the will of the people."
Interesting, but that's not my read of "liberal" intent. Republicans (not your "conservatives") are constantly trying to tell people what to do. The liberals often do as well, but not here. The problem is that it is impossible to enforce the absence of a law: you can't just say "let's not make a law." The winner of the fight over whether to control marriage or not is the one who passes a law saying "Marriage is defined as [blah blah blah] ...". If liberals were trying to control people in the way that conservatives are, they would tell you whom you must marry. Instead, they are trying to create a law that guarantees you the power to make your own choice. Is that conservative?
[Abortion:] Neither side is really taking the position that a progressive vision-of-society should trump rights, although each side thinks the other side does, since they disagree about whether or not a fetus can have rights.
Interesting... but Ch. 4 of Freakonomics makes a strong case that if your Grand Vision of society values low crime rates, then access to abortion is critical. So, yes, if you believe Levitt and Dubner, then this debate too can be cast as you've cast the ones above. I can't do their argument justice here--the very short and vegetarian version is that women tend to be good judges of whether they're in a position to raise children--but you might enjoy it.
See the Libertarians or the Communists for consistent ideology.
I'm not sure, but I have a hunch that that's because they don't have enough power in the USA to have to deal with actual issues. How would a libertarian handle global warming / ozone hole / etc? How would a communist handle human laziness?