Hi Dan,
I don't think it would make sense to develop such an AsciiDoc plugin
as part JBoss Tools. Indeed, AsciiDoc is not useful when it comes to
developing applications that leverage JBoss software.
However, this could be a standalone project (available through
MarketPlace) or a support for AsciiDoc in Mylyn WikiText. You could
open a request here:
https://bugs.eclipse.org/bugs/enter_bug.cgi?product=Mylyn%20Docs .
Maybe that's something you could request to the AsciiDoc community
too.
HTH