The best defense is a good offense and the swarms would protect the crewed tank the best by allowing no LOS no effectively the tank can remain a indirect fire/BLOS platform
In a world where you can shoot indirect, so can the enemy. You should not expect to outrange a technological peer without dedicating it in design.
A vehicle a fixed maximum weight budget, for example 50 tons, with a crew compartment of 10 tons and chassis of 20 tons, leave you with 20 tons for weapon of X range on top of other chassis weights.
A vehicle with sample maximum weight budget of 50 tons without a crew compartment, with chassis of 20 tons leaves with 30tons for weapon of X+Y range.
So sitting the crew in another vehicle result in more weapons range.
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But that kind of thinking is highly attrition and tactics focused. If you look at the current war, huge losses are taken in offensives that everyone knows is "inefficient". But moving into no-man's land and taking huge losses is necessary: long range fires can not neutralize all threats. No long range fire can deal with mines, and long range fires are extremely inefficient against small platforms in complex terrain.
Perhaps much of shellfire can be replaced with indirect, but there is no solution to mines or tunnels or obstacles and one has to close to minimum range at some point. Armored vehicles have to do.
Armed swarms operate in airspace too difficult for adversary CAP and they could down helicopters themselves.
Defensive counter-air can be attritible drones themselves. The opponent will have acceptable some attrition as price of maintaining battlefield control.
Swarming UAS/loitering anti-tank munitions are going to be operational-tactical systems used by division or brigade artillery units for mass anti-armor fire in lieu (or probably in support of) systems of conventional anti-tank means such as smart artillery shells and TGSM rocket artillery.
Loitering munitions are anti-concealment weapons, by being able catch short windows where the opponent moves. The small aerial vehicle space has a lot of designs available:
1. Loitering munitions
+sensors/comms
+endurance
-speed
Some alternative roles for small aerial vehicles can be seen:
2. Low cost cruise missile (Iranian shahed "drone")
+ endurance/range
+ warhead payload fraction
- no sensors/comms
- speed
3. Low cost bomber
+ sensor
+ reuse/VTOL
- endurance (20 minutes, <10km range)
- speed
4. Missiles (rocket powered)
+ speed
- endurance
I don't think loitering munitions would be optimal in swarms or in massed fires on protected frontline forces. There is too much sensors expanded with excessive overlapping coverage, and long endurance is not needed for tactical distance attacks. The need for mass also suggests the target force has hard kill defenses and while lacking of stealth, where faster projectile works better.
Basically, if the opponent is trying to rerun of Prokhorovka while massing AA, it is the place to use to time on target attack with MRLS/Artillery. Perhaps drones can be allocated for this task if other assets are unavailable/insufficient, but it is not optimal.
The real utility of loitering munition is killing opponent forces trying to infiltrate the front lines, or attacking rear line assets doing shoot and scoot out of hiding spots. Basically where sensor-shooter separated kill chain is too slow and the target to hide before fires can be applied. Of course of the opponent lacks basic AA coverage, everything else can be engaged too, but the opponent simply will not survive against drone mass if they lack AA in general.
If the opponent position is known, for example front line facing each other, bombers with very short range is sufficient as long as it can penetrate defenses. That electrical quadcopters can do this role is illustrative, I think the evolution of the concept is high speed electrical aircraft (low operating costs) doing dive bombing while normal ISR is offloaded to other platforms, as cycle time, weapons accuracy, and defense penetration is important here while time over opponent is low.
The counter system is provisioning mobile platoons and companies with local air defense systems able to defeat one or two drones at a time with airburst grenade launchers or lightweight cannons that can fit into an RWS and be guided by vehicle self defense radars.
I can totally see future loitering munitions having a terminal rocket dash stage with wings ejected. This is not unlike Russian AShM with supersonic terminal dash. (or mount a rocket, for the larger platforms, already seen on some large multicopters)
Basically attack munitions will evolve to defeat defenses, but do it in a matter that minimize costs. If air defenses only works for self defense against slow projectiles, air attack would evolve fast projectile in the terminal stage. (complex network attack is a expensive counter and not needed against lightweight AA guns)
Now some formations already have far more significant defenses, but if independent maneuver elements are only provided with light AA guns, attack munitions that can defeat light AA guns works to defeat them.
The only interesting thing that autonomous swarms offer is the ability to loiter in the battlespace with on-call massed anti-tank/anti-position fires...
Autonomous and swarms are both overrated. The ability to maintain sensor coverage over huge part of the battlespace is strategic. The ability to combine with other long range fires performing DEAD means no-mans land can expand dramatically as anti-drone AA fail to survive good old artillery.