I'd like to respond to this specific point:

Weld has no way to identify the correct TCCL (container-specific) which should be used.

I was able to get the test application I sent you working with this proof of concept code.

With this change weld was able to correctly identify both classes and assign them the correct container-specific TCCL. Given that this proof of concept works I believe it's worth discussing the strategy of acquiring the TCCL from the observer itself before we say that weld is unable to identify the correct TCCL.