If you were to adopt a set of rules like that, you need to be strict with their enforcement.
For example, on another forum i go to, they have some similar rules. If you omit one of the requirements, a moderator will post and inform you that you need to complete the post by the rules, and give sthe seller 24 hours to comply.
If they dont - thread gets deleted.
You could always have a template or layout under the rules. The seller then copies the layout, and pastes it into a new thread, then simply adds their data.....
Sorry, maybe Im getting carried away, but just throwing a few ideas out there ;)