My idea for changing shields is to make them function more like hull. I think shields should reduce incoming damage to the hull and internals, with their own armor hardness that stacks on top of the hardness of the hull. Shield hardness could work like resistance, in that it would be a trade off between hardness of shields and overall shield hp, this would mean that a prismatic shield engineered for high base hp would reduce less damage to hull than a regular or bi-weave shield engineered for resistances and hardness.
Having shield hardness stack with armor hardness could also give more use to the focused engineering effect on energy weapons, so you could make a build specifically to pierce through the low hardness shields of a traditional shield tank to attack the hull directly, giving a use to mirrored surface composite hull as well.
breach chance and damage could also be affected by shields, with higher resistance meaning higher breach chance and damage reduction, and with the converse applying as well.