If you want a defensive screen: minimalistic gliders, deployed to high altitudes, that dive down onto a target when needed. They'd simply use altitude as energy storage, and when that's nearly used up they take the rest to make it to some designated landing field, ready to get collected for the next launch. Multiple "shifts" at different points in the altitude cycle at any given time.
Sensors fly separately from the consumables, hitching the same ride up. The consumable ones only need their own for final approach which might even be assisted by "painting".
A bigger problem would be sensor overload from all the friendlies, you'd probably want those loitering to follow a course determined by a PRNG predictable to everyone who knows that day's key. But that's just very basic crypto put to novel use.
Maybe you can have a big "carrier" drone transport them to where they are required, like in StarCraft.
Or maybe you can make the small drones recharge directly from the grid, by landing on top of power lines and deploy the necessary connections.