So maybe we could revise some explosive ammunition instead of using a design on it. It'd mean no AP shell this turn, but if the Crystalclad comes out of the oven well done, then we may not need the AP shell immediately. I'm still heavily leaning towards the AP shell but I'll see once we know how the Crystalclad turns out.
Future(?) Revision: Blastgem
We've had experience with anti-magic arrows. Made using crystal in the same manner we use our anti-magic charms and magegems, they're unstable enough to explode in magical contact. This proves that we can utilize magegems' explosive potential without converting it into things such as fireballs. The presence of too much magic in a container leads to an explosion. Our anti-magic arrows were notably weak because of their containers' low capacities. But using the storage of an AA-sized magegem, we can fill it up to the brim in capacity allowing to unleash a sufficiently devastating explosion.
The Blastgem is a simple revision to the Magegem. We add a basic "timer" circuit (we've done much more complicated things with circuits in the past) to a slightly overcharged AA-sized Magegem. When the circuit is activated by a very firm touch for multiple seconds, it activates. The circuit will tick down, and once it reaches zero, will cause a "spark" in the overcharged magegem, making it explode.
TL;DR: We make a grenade by overcharging a Magegem. Then later, we can revise this grenade using our experience with the Equalizer into an explosive shell for our artillery, freeing up a design slot that we would have had to use for an explosive shell.
The Blastgem is immediately useful in close-range/melee combat, as any of our soldiers can use it as a grenade. This makes it have some use now, but their artillery is still dampening that fact. But, using Blastgems and experience from the SO1-AM Equalizer (anti-magic shell), we can revise the Blastgem into an explosive shell. So if we were to revise the blastgem this turn then the explosive ammo next turn, we would be able to use next turn's design for something else. Sure, it's not a fireball, but I'm worried about overinvesting in the department of fire, since it is something that can be countered.
Perhaps even better, this serves as a huge stepping stone for other things like Firegem, Chaogem, Lifegem, Frostgem, and more.