I was thinking of something like the following:
Testudo
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Some units have carefully drilled and practiced an ability to arrange themselves and their shields in such a way to provide extra defense against ranged attacks. Historically, the Roman Legionaries were noted for this capability.
Activating a Testudo formation for a unit with this special ability is a special reform order.
The unit is arranged in a double column formation, with the two elements side-by-side in the front, and each successive element in a rear hex-side of the element in its front hex-side. The other front hex of the unit should be facing to the side, out from the main body of the Testudo.
It takes a reform order to deactivate Testudo.
Once a unit enters Testudo, it must remain in the formation for the remainder of the Turn that it activated the formation. Units that begin a Turn in Testudo, may deactivate the formation at any time during that Turn.
Units declare they are in Testudo formation for that turn are considered to have +2 ranged attack defense, but cannot move more than 1 hex per turn. The only valid order to a unit while active Testudo formation is to Move - they can neither declare a melee or ranged attacks, nor may they Reform - accept to deactivate the formation.
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Thoughts?