What about this approach: When troops (or vehicles) need to relocate/move so they are more open to attack - a mass of defensive fpv drones (or AI assisted swarm drones) are moving with them. Those drones must have some sort of sensor. Probably simple optical cameras and microphones - as anything else might be too expensive to scale up massively and would draw too much battery. So range of those sensors might be sort of similar to human sight and hearing. For better performance, drones could communicate between themselves and share sensor data - though again, that might end up being prohibitively expensive or power demanding. We're still talking maybe a 100 meters for interception, probably not more. Sure, some attack drones would slip past - but idea is lowering casualties, not stopping them completely.
The idea simply being that when an unknown drone is detected coming too close to your assets - the defensive drones intercept and detonate close by using a very light fragmentation warhead - still likely lethal to a drone from several meters away.
There would have to enough such drones, of course. As those defensive drones might still be more expensive and less available than regular attack fpv drones. You'd probably have to plan movement very carefully - so a protected area is reached before your defensive drones run out of power. Alternatively, replacement additional drones would need to be sent in, periodically.
Besides technology potentially not being there to work at scale and at desired price - another big question is whether you can count on having more drones than the attacker. If you have a 1000 km frontline, but you're making a movement with your troops only at 10 places, along say 20 km of the frontline in total - would that allow you to focus your defensive drones (which are probably not numerous enough to go alongside the 1000 km front all the time) on those 10 places and still outnumber the attacking fpv drones - because while those are cheaper and more plentiful, they are still distributed in units alongside all the 1000 km of the front. So localy and temporarily - the side using defensive drones might have more of them at hand and enough to do their job?