When the "Old" 2.0 was the in the making it was often stated that it would be a lot easier to add new questions types comparing to the LS1.X codebase.

What is the situation with the "New" LS2 codebase?
Will it be a plugin concept, which will help "casual" codes to be able to offer new questions types without being a core developer?

As an example I choose this workaround.
docs.limesurvey.org/tiki-index.php?page=...axDiff_question_type

This questiontype is similar to a datastructure of an rankingquestion where you can only choose two ranks from n ranks. Additional textlabels for max and min and a radio button layout make the difference.

A freeformat question type could be an alternative to creating many new question-types. How low can the entry barrier become?

LimeSurvey 2.0 (the new version) is mostly a plain port from LimeSurvey 1. That means that question types are not object-oriented yet and it is not easily possible to add new question types yet.

However it is planned that we will move into that direction step by step. When thy groundwork is done we will certainly move and make question types real objects which you can inherit for your own question type.