This looks interesting - I've begun to test it; thank you.
I'm also the developer of WordShell, http://wordshell.net. This plugin has a Version: header like this:
Version: beta 1 (0.6)
I and other WordShell users have tested hundreds of plugins from wordpress.org, and we've never come across a version format string in that format. You may find various tools out there can't parse it or are confused by it, as it's a new thing. I've seen ones like 0.6beta1, but by bringing in a never-before-seen format you may break some things.
I fixed up WordShell to partially handle it, but generally best practice is to stick to numbers only, have no spaces in your version string and if you really must have a double-scheme (two versions: firstly it's 0.6, secondly it's beta, and specifically beta version 1) then use one like 0.6beta1.