So here's the deal. When knockers, the smallest gremlins, hit their little wands together it causes an elemental explosion. The wands are color coordinated to the mineral scheme to build gates; the ice knocker for instance has blue and green on his wands, because that creates ice. The fire has red and yellow, for fire, and so on.

Exploding two shard bombs in an overlapping area should generate the corresponding explosion.

Whenever two shards collide on the ground, they should explode instantly and cause a special effect. Gate construction gives 4 statuses and 6 families. Obviously, the 4 statuses would just add a strong chance of strong status to their mixed explosions, but what about say, a construct flavored explosion? Those would deal a ton of knockback, and cause a special effect.

Gremlin = Red + Blue = Missiles drop down, like from the artillery pickup.
Construct = Blue + Yellow = gears fly out, extra elemental damage is done, tiny chance of creating a friendly mecha knight
Slime = Green + Yellow = spawns a single explosive jelly fragment that damages enemies and not the knights.
Beast = Red + Green = random bite marks appear, extra piercing explosion, beast bell sound is heard occasionally
Fiend = Red + Purple = Shoots furniture out at random angles
Undead = Yellow + Purple = Curse status is added

From an awesome perspective, this would be gameplay.

New Blue Shard Bomb!

The new blue shard bomb would be a second elemental shard bomb that deals less damage and sleep. It could do something else, but the important thing is that it's introduced so as to make these changes work. :D

Reference: https://wiki.spiralknights.com/Gate_construction