To be honest I don't see a need to make every mission different. Yes, it's a fairly standard infiltration mission. What's wrong with that? Infiltration missions are fun.
...
for a reason and to a varying degree. This one is not, due to the setup. You can stretch suspension of disbelief to a point, but x-com wearing animal furs while going up against a fully armed and armored strike-team is defintely something that does not fit the narrative.
If this was part of an elaborate plan to abduct a contact it might be believable. But X-Com starts out completely exposed, facing off mercenaries and trusting in their bare skin to block bullets (or rockets). X-Com arrives, disembarks and attacks immediately.
At that point, what's even the purpose of wearing the disguise? During beach+winter missions X-Com starts out in buildings - meaning the disguise was necessary to infiltrate said locations. As a result your agents also start out in cover (more or less). Industrial espionage has enemies that are lightly armed, mostly with makeshift weapons due to the setting. Which fits in with X-Com going in unarmored - your agents are - if anything - only slightly outmatched. With this mission there isn't even any explanation in the briefing that something has gone wrong or how that plan was supposed to go off (compare the "meet the informant" mission).
It's not even clear why the disguise is needed in the first place - I guess X-Com sets up the meeting remotely (otherwise they could just nap their contact there and then), drives up in a Van (with tainted windows so no one but the driver would actually need to be in disguise?), gets out and then...demands that the mercenaries submit and get in the van? This is at least missing an explanation as to why, exactely, X-Com is starting off in a shooting gallery, outmatched and with no backup-plan.
It is indeed not normal, but in this case intended - for political reasons. I think the UAC arc kinda answers that if you get deeper. They are probably not okay with that, but they have their circumstances.
But why is X-Com going in guns blazing if you are (originially) only supposed to "arrest and interrogate" their personal? Shouldn't this also be a mission that has weapon restrictions, seeing how you are also facing unarmed civilians? The engineers working at that site aren't even involved in anything illegal, going by the interrogation.
Why is X-Com concerned about interring some human bones they find in a cave, but has no qualms about shooting unarmed and innocent civilians?