Here is the whole story:
1. I have an abstract generic base entity in another diagram..

2. When I drag-n-drop it as a simple link to another diagram..

3. And I generalize a class from this base class and bind the template, everything is great..

4. Now, as I wrote, there will be a lot of classes so the diagram will be a mess, so when I delete the base class just from the diagram as you suggested, nothing happens, no italics nor anything..

5. So I tried directly to generalize a class by drag-n-drop..

6. VoilĂ , the base class is in the element box as italics, hooray..

7. But where is the template binding, I tried to add one..

8. And this is what I got..

A really appreciate your efforts but unfortunately what I am trying to do is a bit different and I still hope that there is an answer for this problem. Thanks in advance and sincere regards.