The packageformat is entirely static. A series of plain-text files with fields separated by lines and spaces. Easily parseable via any programming language or with basic UNIX utilities.
And you have to write parsers for it which is PITA even if it's very simple.Please just stick to well-known formats (even if you don't like them) and make your fellow developers life easier! For example, everyone hates YAML for one reason or another, but if you use it, you are using a format everyone is familiar with it. We know it's terrible quirks, but still well known and every language has parsers for it.