[TYPO3-mvc] How to extend a model class from within another extension?

[Franz Koch]

Hi,

> For the meanwhile I added the new getters and setters to the
> already existing extension (ExtOld) which results in the fact,
> that the extension is not updateable anymore in future.

how about implementing magic setters/getters for any TCA defined column? 
But I wonder if extbase would fill the class vars properly - might be 
worth a try until extbase has a default feature/way to do this.
-- 
kind regards,
Franz Koch