Testudo Legionaries

[A Terribly Harmful Name]

To answer the OP, there are currently no plans to include the testudo, as you noted, that method replaces another formation. At the same time the practical application of the testudo was severly limited we find it used mostly in siege assaults.

Or in the very famous Battle of Carrhae.

So in sum...

There can be no historical Carrhae without the Testudo formation.

My two cents. I would really like to see it in EB II.