Ok, I'm going to take a stab at this.
We're a bigger site than Sports.SE (by a good bit), so I'm guessing beyond just a call for questions, we should probably make an effort to try to treat this more like a new product push on Arqade complete with limited prize support and if possible a community supported site redesign (GN mentioned SE not wanting to allocate a minimum of developer and designer resources, if we do that ourselves it should fulfill that requirement).
to address your points directly:
We need a multipronged approach here.
- We need document in the hands of our users ASAP. Whatever this means, the key thing is having experts on hand to answer questions right away.
- We need to cross post stuff. Ask questions here, then post them in the Wizards forum with a link to the question. If you get a good answer, self answer (or better yet, draw someone in from over there). Let's be careful to not be spammy about this.
- Get the word out. A lot of us are friends with gamers on FB and Twitter. Let them know that the best place for high signal:noise Q&A on 5e is right here.
- We need to make sure this site looks like a great place for 5e questions. That means a proliferation of content on the site, questions getting answered and maybe a temporary redesign to get us started
Design stuff. This is the big question, and ultimately, it's probably up to us to design the art, vote on any potential designs and ask SE very nicely to implement. Things we need to know going forward:
- Will SE let us use fan art as the site header.
- If yes to above, what dimensions would said images need to be.
- What design elements should we include to make it feel like 5e's home on the web.
- What license restrictions are we operating under when creating this. How do we make it feel like 5e without stepping on license toes.
The ideal thing here would be for SE and WOTC to develop a promotional relationship. However, that is not something we as users have any kind of control over. Thus it's best for us to operate under the assumption that this will go on without WOTC's official blessing or support.