I had a look at WebCT and IMS QTI.
WebCT should be easily accomplished but it does not fulfil our needs.
However, IMS QTI seems to satisfy our needs but, as you said, the complexity is too impressive so there is no way I will be able to implement it within the time-frame I have been given.
I will probably keep on implementing the import mechanism for a file-format that is ruffly the same as above. Even thou this file-format eventually will end up as a dead end, the other framework I implement for a new multi-answer question-type could prove useful in the future when we start parsing the IMS QTI format. Therefore, I still hope that my future multi-answer contri will be accepted.