Kos is actually a libertarianish democrat. For example, he supports the Second Amendment.
There is no such thing as a "libertarian democrat". Even if such a creature existed, I'd be curious to know which parts he supports.
To be honest though, some important issues like the 2nd Amendment and the issue of life or death (abortion), there is no middle ground. Either you're for gun ownership it or against it. Either you're for life or against it. The middle ground is for those who like to meddle around in gobbledygook.