I may be getting a bit ahead of myself thinking about performance at this stage :-)
The problem is that according to the spec Weld has to fire ProcessAnnotatedType for every class in the bean archive. Weld does have a non-portable extension to limit the classes that are scanned, but in the general case there is not really any way around this. Even if you could build the meta model from other sources without loading the class (which I am not sure is possible), as soon as portable extensions enter the mix you are almost certainly going to have to load the class anyway.