Decoy Trooper is a cheap offensive mid-ranged combat strategy (or simply put, a role) available in MiniTroopers through means of specifically aligned upgrades. The sole task of a decoy trooper is to break ranks and draw enemy fire, essentially saving the rest of the troops from area of effect weapons and sniper fire, at the same time, giving long-ranged troops a chance to attack with little to no retaliation. Naturally, for this to work one just needs to lack any long-ranged weaponry. However, facing more sophisticated armies, decoy troopers will need specific upgrades, such as Bait.
Even though it's tempting to load up as many Troopers with Launchers as possible, lack of decoy troopers may often result in quick decimation with the very same rocket launchers. Also note that after sophisticated upgrading a simple decoy trooper can evolve to a Shock Trooper.
Nevertheless, the whole effort can be spared with a right placed Clown Grenade.