[Edi]

An Iron Faith / Black Forest mix of units is not at all inappropriate, since thematically it makes sense that a pure BF Ulm is the end result of a blood cult corrupting the Iron Priesthood that had supplanted the Master Smiths of Ulm. Such a mix would be from right before the Malediction or very soon after it before the remnants of the Black Order disappeared.

As it is, themes as they were in Dom2 no longer exist, each one is a separate nation. However, nations are probably tied to eras.

Edi