that was a suggest
Imagine like have to place dynamite in a tunnel, have to seal tunnel with some dirt or stone and then trigger the placed explosives on click (like opening a door by user)
The effect were somewhat similar to magic explosion but not in exact the same pattern, more like how many foreground-blocks surround the dynamite and how durable the surrounding blocks are - the more walls around the more pressure it will build up into directions where weaker foreground-walls are, if dynamite not enclosed from all sides the blast will be fruitless concerning mining and only damage creatures & dwarves in open direction nearby - i think you know what i mean, so player has to plan his explosions carefully.
Also fishing: let dwarf place dynamite (not enclosed by walls) onto a block that is adjacent to some fish & water-containing area and the blast will "kill" all fishes in a certain distance so the fish only has to be collected. Other creatures or dwarves near the blast will get damaged of course, use carefully...
And cannons i imagine could use up a lot of iron, damage multiple enemies at once (high collateral damge) so of not much use for single enemies but for the masses (as fireball), but more durable than tesla or arrow-tower if under attack.
Perhaps user has to click or enable the cannon to fire at all and each shot will cost one "cannon-round" (cannonball, some gunpowder, a rope and a torch) from the stockpile. If no rounds/bullets available, cannon can not be used
