My thoughts: Human/Merchant just going for the specialist bonus and building credits. Although Human have -10% gain.... they wont be effective unless Max gain everytime they hit. Chaining would hurt.
So, their role, I would say should play a free attacker role. Whoring and max gain.
Although to counter this is to chain them down first, but still... if you got more than 5 Human/Merchant prov. It should be sufficient to be a pesty bug that will skew the strat of the opponent.
You may wanna play Home strat. Because likely you will be the fireball target.
Summary: Human/Merchant is a hybrid, not a full attacker role. More so as A/m