The macro syntax is interesting. It's a bit like XML but with attributes that aren't quoted, vertical bar which delimits attributes, and uses braces instead of <>. Also, there's no special syntax for ending the tag (it's not {/code} but just {code}). Which tags are multi-line must be hard wired based on the tag name (i.e code macro is multi-line).
We can always make up a file extension and map it to a language. Seems like the Language name should be "Confluence Markup" or "Confluence Wiki Markup". Extension could be ".conmarkup" but you will be able to add others.
Given that fact that there probably won't be many customers using whatever we put together here, I can't promise we will add this. At a minimum, we would have to cut corners and leave out XML-like color coding for macros and embedded language color coding for "{code language=Java}...{code}". Even with leaving this out, a simple color coding profile (a bunch of regex config stuff- not writing code) and a tiny Slick-C macro for tagging headings would go a long way. The tag headings Slick-C macro would be similar to markdown_proc_search() which is very few lines of code.