Specify order of attributes in crosstable
Ok, I might have found an answer myself. 
I learned that I can "emulate" the table generated by the second query by this:

$$VALUES ('MR_Type'), ('groundTruth'), ('origin')$$

This way I have control over the order. And if anything changes I have to add it into the AS statement nevertheless.

I don't want to eliminate the possibility to use maybe another special purpose table to control this mechanism, but for now this would be ok.