I would like to see the addition of a shield using the new turtle shells. I have a couple of ideas for the implementation, such as different levels of material requirements based on what tier you would want it to be on.
For example, if it was to be on a similar level as the wooden shield, then the recipe would simply be;
4 x Turtle Shell
4 x Leather
1 x Bone Glue
Based off of this tier, the shield would have similar or lesser wear, I lean towards lesser, say Q/13 * 75 for wear, but increased deflection, for example sqrt(Q/10) * 4, or perhaps by 5 depending on how the numbers end up working out.
If we were thinking higher tier, then the materials would increase;
6 x Turtle Shell
4 x Leather
8 x Hard Metal Nuggets
1 or 2 x Bone Glue
I would suggest this would require different skills for the softcap, but other than adding smithing and requiring it to be made at an anvil if you were to decide this was the better option I'm not sure on this. Perhaps just carpentry and dexterity for the first option and just add anything for the second. Not entirely sure how the wear and deflect calculations would fit into this second implementation but I would expect that the wear would be brought up to the same as the wooden shield and the deflect would have a small increase over the first implementation.
Thematically I believe this would fit in to the world since in a harsh environment you would expect to be relying on not getting hit at all, parrying blows where possible and a smaller, curved shield makes this much easier, along with being something that would be mush easier to carry than the large roundshield we have now. Large shields are good for set piece battles and large volleys of arrows but personally I feel our hearthlings would be trying to avoid damage rather than taking it on the chin where they could.
TLDR; New turtle shell shield, two different possible tier implementations with higher deflect and lower wear.