Other than the potential of it being unbalanced, which everything has the potential to be, I'm not seeing the Armageddon you're describing. This is a thread for ideas, if the numbers don't work, they can be tweaked, if the burst radius on weapons turns out too large, the rounds can reduce burst size.
Say I take your ammo and apply it to Hades.
As for your Hades example, you've taken one of the heaviest weapons with a large burst radius (which is obviously what this ammo would work well with, not a Mercury Field Gun), which just so happens to fall in an arc which, except at close range will almost always drop on the balloon (where no one will ever be.) Even if you did hit the hull, you would have to catch a character in the effect range,
and they would have to be unattached to a gun or helm (which even engineers can man). Furthermore, there is never a guarantee that it does anything at all. Even if you were say that 1 out 4 shots definitely moves a person (and that would be untrue) there's no guarantee that they they're blown off the ship or even that it had no effect on their performance because they were in a 6 to 9 second round time from just hitting a component with wrench or mallet and thus able to realign with no effect of their performance. Also, if your gunner is dropping 4 mortar rounds dead on where it would catch the same area, then they're a crack shot or you're right against the enemy and you should be going for damage.
As for hindering a gunner; against this ammo, a gunner is actually less likely to ever be unattached from their weapon since these rounds would cause reduced damage to the gun they're on, meaning they're less likely to get thrown off when it's destroyed or spend more time unattached repairing the damage, since it would take half as many swings to fix any damage, and that's just using a -50% damage example. And that's before even factoring in a 3 in 4 chance that the round does not even affect them.
Mines and Lumberjack using that effect on players... No. End of discussion.
Sorry, no. Assuming that it takes 4 hits to 'proc' the 25% chance of Concussion, then your ship just flew into 4 mines. You've got a lot more to complain about and it has nothing to do with this ammo type. Even then, you've only taken the damage of hitting two mines. Also, this ammo has no affect on the mine launcher's clip size since it fires one mine at a time. I don't even think you could
try and hit 4 mores on purpose to make your example even valid. If your assertion is that your opponent is able to pinpoint 4 mines into your flight path through sheer skill then they would be using normal rounds for a kill, not these, which are a delaying/attrition tactic.
As for the Lumberjack, that's a primarily balloon disabling weapon. Since it's highly unlikely anyone's standing on the balloon, only a hit on the underside of the balloon
might affect someone (depending on ship configuration) Since mortars arc down they're more likely to land atop or along the side of the balloon. There's a chance you might claim you could cruise under and fire upwards to catch the target as the mortar rises but then you're likely getting within the range where the mortar has no AoE. But taking it to the extreme, that you're an expert marksman and do land a mortar on the hull and it has a burst radius... Great! That's what this ammo is for. Except you just did 50% of the already low direct damage of the weapon to hulls and components (and cut it's phenomenal damage against balloons to half) and have a 1 in 4 chance that maybe an enemy crewman get skipped a meter or two over assuming they weren't manning a gun. Sure, the potential is there but the weapons you're using as an example wouldn't be better off than normal rounds.
In fact, in almost
all cases, it's better to use normal rounds than these, which are way less efficient except in a few cases where they
might work well. But since those cases are quite rare or unlikely, that means classes other than Gunners can't risk taking this ammo as their one option. Which means, this ammo type is exactly the kind of example of something only a Gunner might be able to bring to table in a crew. And if it turns out it's not useful, they still have their other two ammo types or normal as always.
That's the point of the thread. There's obviously testing going on and things can get tweaked. I don't know why you would assume that any idea is just going to be tossed into the game slipshod. Other than a claim that 'It takes away character choice!' (Like your choice not wear a safety harness on a flying brick tethered to a gas-filled balloon.) Everything else is able to be tested and tweaked. As for, '...taking spotters away.' There really isn't any reason not to take the Spyglass (rangefinder being the only option.) This actually
adds another choice for anyone other than the pilot (which is everyone else.)