LocalModule, Jython, Metaclass

Bonsoir,
if I'm not wrong, while it is possible to add stereotypes and then tags, it is impossible to add metaclasses in the local module. Is there a reason for that?
I'm looking for a cheap way to add tags on existing metaclasses *without* defining a stereotype, and this from jython. For instance to add a 'length' tag on all uml attributes. Is there any possibility to do this? I want to avoid the burden of defining a module, compiling java, anting, etc.

Currently I'm squating the local module from jython, but the 'no metaclass' limitation is quite annoying . And this is the same from the end user perspective: it is so cool to have a local module, but a bit frustrating to see this limitation.
Any wordaround appreciated.

Cheese,
Jean-marie