I agree, one "assessment" which is the current complex UI and one "survey" mode would probably be enough. Also we could think about reducing the complexity by making good guesses when a new question is added (aka: the default ones), and let the user edit the parameters if he wants to see them changed.
Last but not least, currently the assessment system has (had) the major hickup that it was nearly impossible to edit once entered data. I took care of that one for one of our clients.
Once Heidelberg moves to postgresql I'd suspect that some effort can be put into making all the nice changes from HEAD (not sure what has been backported, I'd count better performance and lickert scales among the major ones) work back in the postgresql 5.2 version of assessment, while retaining any changes done in your simplification work.
