I recognised your question because had the same earlier. It would be nice to have a dictionary with meta data to have oversight and it would be smart if we can configure our loads from it, as you mentioned.
With help of forum members i managed to get it working. See attached example of the data dictionary in excel and a script example in a qvw. The solution is bases on mapping loads and rename fields. The automation of the SELECT statement is based on a variable (Relevant), loaded from the DD sheet. You have to be aware to just load the plain data in this first step, no adjustments or transformation. That's wat i did in the second step, so you have also to consider a good matching architecture here.
In the Data Dictionary you can also store and manage your variables.
Have a look at the article of Barry Harmsen on storing variables outside of QlikView on QlikFix.com
It would be nice if QDF and above could be integrated, but i am not so far yet.