well no clear yes/no answer to this as I need to understand the objective of the exercise better. My take on it is:
If you are seeking to create a nice class hierarchy, then mind you that inheritance only takes the methods, not the template. So if that is what you are looking for (inheritance of controller logic), then your example may be a nice starting point for an abstract class. (although it lacks the class definition itself, so it is not complete).
If you are looking for different templates , then inheritance may not do the trick for you as I believe templates are not inherited in a way that you can enrich the parent.
Going back to the original question/comments from @fOrtiz :
how to use a single Modal class to every need in the app. Or if that is even possible. Does Ionic require us to define a Modal class for every different html resource?
I find the above difficult to understand, as I don’t think there is such a thing as a Modal class. What you typically do is: create an ordinary class, decorate with @Component (or @Page etc) and then use the ModalController to present it. And yes, you need to create a new class/Component definition for each different HTML template, unless, of course, you use data binding, template directives and all the nice goodies Angular gives you.
For that I suggest everyone starting with Ionic, first to go through the tutorial @ angular.io. Most of the questions new people ask on this forum are actually related to angular.io and a lack of understanding of its architecture. Including difference between @Component and @Injectable.