3 of the 4 guys on Mount Rushmore were surveyors. Surveyors love the number 3. Triangles are inately accurate geometric figures. The US government is a triangle for this reason. However, if you add another node, and it connects the 3 preexisting nodes, you then have a tetrahedron. A tetrahedron is a very strong figure in 3-space.
In general, the branches of the US government can be arranged by timescale of concern. The executive is concerned with immediacy, constantly. The legislature is concerned with the middle term, annually, and seasonally, and the judiciary is concerned with the permanent, when they perceive it as arising.
The idea with the Advocary College is to be concerned with the spurious and intermittent, and to attempt to create it. (Jan 2012) A very good way to create the unexpected is to educate people.
The powers given to the Advocary College are mostly closely constrained. They can indict a President. That's a long way from convicting one. Another basic idea here is to put the gripes in the government, where their gripes will be heard. The US government is so big now, it should in a sense contain some outsiders, formally. Thus, the College is almost randomocratic.
Another way to look at it is like subtractive synthesis. In music synthesis, you can build up sounds from sine waves, which is additive synthesis, or you can filter noise until you get something interesting. The existing government is additive synthesis, but the source sinewaves are pretty sloppy. In general, something needs to be added to the mix.
On the matter of a national correspondence school, (Hi Sam!), that gives them something to do if the President doesn't warrant indictment, and it jibes well with not requiring a college degree for anything.
Having their own route to proposing Amendment will help fix any problems or glaring opportunities that arise.
And for some things, like pardons of executive branch people, just having one more branch looks pretty handy.
As early as Aristotle governments were seen to divide naturally into three branches. I still think another one can be worthwhile. I'd like to do something on government secrecy based on the Advocary College, but I haven't worked it out yet. The AC gives a sliver of parliamentary representation to the US, where minor parties get a small but ineraseable voice. If an issue comes up that the other three branches aren't facing, the AC can bring it to the fore, and in quiet times, they can involve themselves with the correspondence school.
I think a correspondence school is a good role for the federal government, as opposed to the Dept. of Ed. telling States how to run their schools. Don't bother. Just provide a federal alternative. But I've also got a "No Child Lugging Books" program in issues/platform.html, so the D of ED isn't on my chopping block entirely.
Most of the US Constitution is drawn closely from Anglo-English precedents, but with some re-purposing. The AC is something of a flight of fancy, but does have some precedents in parliamentary representation by party, standing grand juries as in California, and maybe some other stuff. [Oct 2011] I'm better than I thought. Madison himself wanted something like the Constitutional review of new legislation function I give the AC. He wanted a body just to do that. I saw that in Storey's or Putney, 1908.
The AC also acts as a consolation prize for national candidates, which can be a good thing.