I'm in the process of converting MapleTA questions into a format which can be run in native Moodle. This will probably end up as a combination of Moodle multiple choice and STACK questions. The import will only be partial, and the resulting questions will still need a lot of editing, but much of the tedious copy and paste will be eliminated. E.g. question names, and question text will be imported and place in the right Moodle question fields, ready for a human author to edit.
Would anyone else value this work? If so, I'll consider working this up into a Moodle plugin (currently have only skeleton PHP scripts I'm planning to be a one off use!). If someone else would like to collaborate and help develop this then so much the better. Please feel free to message me off the list as you prefer.
Chris