It's been a while since I posted the thread, but a collegue of mine returned last week and after a little research we were able to create our preview by using Pydev and python.
Via a little programm we let AsciiDoc handle the generation of a html file and then we let Eclipse open a window to have a look at the generated html file.
It works pretty well and now we are planning to go one step further, we are trying to implement syntax highlighting for our editor, but of now we are pretty clueless how to go at it.
At the moment we are looking through different guides, mainly wiki.eclipse.org, but with no real luck of finding anything useful...
That's why I hope someone is able to help me/us or at least be able to send me into a direction... Thank you!