It is safe to use same classes from same modules in different layers

[PavelTurk]

Alan, could you please tell if it is technically possible to substitute classes from another layer for an instance?

I mean for situation with three layers I described :
Bootlayer (module Core) is a main application
- child layer A (module A, module Foo) is a plugin A
- child layer B (module B, module Foo) is a plugin B.

If class in Module B gets an instance of Foo (from module Foo) created in Module A, is is possible to substitute its class with class
from module Foo in layer B? I understand that currently it is not possible. I ask if it is technically possible to implement it.

The reason of my question is that real dynamic world is not as perfect as JPMS assumption that if several layers use same module
then this module must be present in their common parent layer.

Best regards, Pavel