I know that UML support is a bit down the road, but as far as I remember, someone from support mentioned that you are already working on it (integrating the free version of the Metanology MDE for UML plugin, if I remember well).
As I wrote in my mail to Wayne, I think, that it would be useful to provide and document an interface for other plugins to be able to call on the modeler plugin to query and manipulate the model in runtime.
Also a documentation of the model files format would be greatly welcome, I think.
This would allow us to create additional plugins which could live together with MyEclipse UML modelling. For example custom database+entity+webinterface+glue generation from model would be possible with better performance and better compatibility than by parsing the data files with code created after reverse-engineering the data file.
Also importing customized, or private notation models from other modelling tools would be possible this way, even if it is not supported directly by the MyEclipse UML plugin.