Currently, if the language variant conversion and content negotiation is needed together, RESTBase will do 2 roundtrips to Parsoid to make 2 transformations separately. That would add a lot of unnecessary latency and overhead.
For the sake of simplicity of the code in RESTBase, it's very hard to merge the transformations. However, we need to look how bad the additional latency is and think whether we should add more code complexity for the sake of lower latency.
If we decide to leave 2 roundtrips for transformations, we need to think about which one should go first