I revive this question because
1) Michael says the Base and the CustomizedClass are not necessary. I could not figure out how to eliminate them. You basically need a customised model, where you override the equation. How can this be done without these additional constructs Base and CustomizedClass?
2) most importantly - How would the example work for several variables/ equations? Let's say you have 3 equations. How can you override only 1 or 2 of them - without redeclaring the 3rd one? Or to reformulate the question: How can a model - including all the equations - be redeclared/overridden by a model which redefines only parts of its equations?
Thanks in advance.