As a Dutch speaking guy, can I enter on this site (if realized)?
Proposal: Dutch Language
Yes; the language sites on Stack Exchange are full of native speakers. They tend to provide most of the answers, while non-native speakers ask the most questions, but some interesting questions about etymology or linguistic features of a language are asked by native speakers. And even questions about typical pitfalls for learners of that language, perhaps self-answered.
Please do! And bring as many other native speakers as you can :-)
In addition to what Glorfindel said I would like to point out that even native speakers may have specific questions: a proficient command of the language does not imply that you can make the rules of the language explicit. After all, most people are not linguists.