Are people actually arguing that these guys are merchants?
Yup. People are actually arguing that. And technically they are. It's just that these folk aren't Empire. Their merchants have to have actual authority, usually taken for themselves, sometimes, rarely, given from another, bigger boss.
Yes they are merchants. Yes, the Skaven probably isn't a Skaven overall Lord, or a member of the Circle of Thirteen. But guess what? Skaven leaders are even more important than human or goblin ones, because of how rare they are with all the constant, unending backstabbing. If you remove one, the backstabbing and killing that ensues will kill more rats than the battle itself. And for the Rat to be fat, he's been in a leader position for a while. Leaders that stay alive among Skaven are even more valuable targets.
In WHFB terms, the Skaven is most likely a Packmaster or a Master Moulder, a Champion unit like Mathilde would be as a Magister, even if her actual magic gear is Wizard Lord level.
As for the goblin, their hierarchy is literally authority equals ass-kicking/cunning. He's probably a Night Goblin Boss, or a Night Goblin Big Boss. In theory he could be some rare variant of a Night Goblin Fanatic Boss, but I doubt it. Those are crazy.
If he's actually the Goblin Warboss, we probably won't be able to kill him, but pissing him off might work just as well. And if he is a Warboss, and we do kill him, expect the defenses of this place to suffer. A lot. IE killing a warboss nets you Victory Points in WHFB. But I doubt he's the Warboss. That would be really, really unlucky for the Goblins, to have their Warboss assassinated before the fight starts. If he's the Warboss, even a gunshot wound to the head might not kill him, and that's without going into all the magic items he would have on him and how they might interfere with killing him. .....
This might actually be the warboss, and we just can't see all his magic stuff because of the damn warpstone teeth, if those aren't a magic item themselves. Hell, they protect him from direct fire spells, don't they? They might count as a Magic Resistance item, or something.
In conclusion, I get people not wanting to risk it. But don't tell me the target isn't an important one. Skaven or Goblin. Or that causing them to think "betrayal!" which is always close to the minds of Goblins and especially Skaven, isn't a goal worthy of risking one's life.
If we manage to start a fight here, we'll inflict as much damage as a full on Battle Spell would on the field. On both sides. That's the comparative risk/reward scenario. Would you cast a Battle Spell on the field if it could kill a Score Stormvermin, a bunch of Giant Rats, and dozens, maybe more Night Goblins? Including possibly a Skaven or Goblin Champion? Maybe both? I would.