For what I'd like to do, (allow Dendron to use other markup system, --ReST, Assciidoc,MyST,ect--), I'd keep the frontmatter meta-data with the file as is where it causes no problem, (think asciidoc allows it), and where it would cause problems, --e.g. Rest at least--, place it in comments and just add logic to dendron to write and read the YAML in a "comment proctected format" that would be activate by file extension in force for the vault we are working with.