I liked your standard. For me, there is only one thing that really bothers me in Markdown and causes me trouble. It's not possible to have line breaks inside individual cells. This is the major flaw in Markdown.
Pure Markdown often falls short when you need fine-grained control. As you mentioned, the inability to freely insert line breaks within table cells is one of those limitations. With lobster.js, you can achieve this by using wrap blocks.