1) There are already sites that hosts Oekaki boards here. Stuff slips through, but it's up to you to maintain basic censorship. E.g. deleting outright pornographic images when you find them.
2) Meh, fanservice isn't a problem unless it's outright pornographic.
3) Yes, see #1, other sites have Oekaki boards already.
4) The activity rule doesn't likely apply, for one simple reason... I'm unlikely to approve an application for just an Oekaki site. The existing ones are side-features on sites where people already have their own art or comics.
5) That's not "paid referring" from what you describe. It's just a domain name, and that's fully supported. See "Virtual Domains" on
http://xepher.net/help.phpAs alluded to in #4, I'm not likely to approve a site just for an Oekaki board. I'm not saying "no" outright, in case you have some new/clever idea you can sell me on, but for the most part, I expect site owners to be producing content. If you have a comic or some such, and a community grows around it, and you want to let that community have an Oekaki board, that's a different thing, but the prime focus of a site needs to be creative content from the owner, or from regular contributors.