Just going to copy-paste what I put on IRC:

<Abculatter_2> An idea for quark: What about dynamite crafted from paper, string, and gunpowder, and changing the vanilla TNT recipe to use dynamite and paper instead of sand and gunpowder?
<Abculatter_2> Dynamite could be thrown if you have a flint and steel or fire charges in your hotbar, crafted with slimeballs to make it sticky and/or ender pearls to make it teleport items near the explosion to the player
<Abculatter_2> Also, you can craft a 'blasting cap' from a bucket, a flint and steel, and a piece of redstone, which consumes dynamite to make a neat, 3x3 hole in the wall it's right clicked on, consuming durability in the process
<Abculatter_2> Also, it could potentially be made to break cobblestone into gravel, then gravel into flint and sand
<Abculatter_2> And maybe be allowed to be used in dispensers

EDIT: As another suggestion I just thought of, you could also add silverfish-infested stone dropping clay when broken, and possibly adding some way to make silverfish not despawn (maybe make it so that silverfish spawned from breaking a block don't despawn, similar to animals? Or maybe having them remember name tags?)
You could also make silverfish blocks occasionally produce 2 silverfish instead of just one, while also making them drop clay when killed. This could give a way for players to 'farm' silverfish in a similar way as animals, but more interesting.

I think silverfish naturally despawn as all animals do, however, they will dig into the nearest stone block when they lose aggro, making it look like they despawned

They despawn as hostile mobs. They are in no way related to animals...
And yes, I know about them digging into blocks when they don't have a target. That's the whole point of the feature.