Implosions could probably stand to have their damage halved to slow them down a bit since 8 mk1s can take down pretty much anything in a relatively (5-10 mins) short period of time, but how they function is fantastic. They're fragile so they definitely need support, so they promote combined-arms. They also speed up certain other tedious processes like wormhole guard post removal/forcefield removal, are ineffective against superfortresses, are ineffective in combat against anything other than a golem-sized ship, and building them is a choice between implosions or another more generally useful ship type since there's a finite resource for spirecraft construction. And yeah, they are a superweapon, so slapping a damage cap on is kind of questionable.
Orelius: Implosion Artillery do damage equal to a certain percentage of an enemy's remaining health.
If a mk1 spirecraft is firing at an enemy ship, the enemy ship will lose .25% of its current health every time it is hit. It's .5% for mk2, 1% for mk3, 2% for mk4, 4% for mk5.
Against a wormhole guard post for example, which has 400 million HP, the damage dealt by the first shot of each mark would be 1 million, 2 million, 4 million, 8 million, and 16 million, and will decrease as the guard post takes more damage. They're basically reverse Neinzul Vultures.