As the Librands roll bar is not on the options list of MMC I don't think it could be possible to get an approval from them.
In case there is no approval for a modification of a car - and if you want to stay on the legal side - in Austria you have to apply for a single approval. For this the opinion of an expert is required (based on technical information like drawings, materials used).
The question is, whether anyone has already invested this effort and there exists documents which might be helpful.
