About changes and/or combining Hero Specializations.

Thank you for the clarification! If this is indeed the case, then even though this option doesn't provide complete freedom of action (you still have to replace something with something else), it nevertheless creates a certain space for experimentation.

Yes. This is more of a "workaround" than a full-fledged method. Because, in addition to the obvious nuances with replacements, it also has negative consequences for Campaigns/Maps that were created before these changes and without taking this modification into account. 🙄
*But it gives some room for Modding, and you can already estimate and dream about what could be assigned to whom when such a thing can be done "properly".