Thats a lot of reply. I will give some background.
The company I work for typically deals with ATEX/IECEX equipment. We design intrinsically safe electronics devices, that go into areas where explosive atmospheres are likely. When we design stuff here, we follow the law, we follow the IEC rules, we follow the national standards, and everything is checked and double checked by a notified body. Otherwise I would've left a long time ago. I personally oversee a lot of these projects, and designed electronics here.
There are a few projects, that dont require this. So this project doesn't go into an ATEX zone. But it is an electrical box that is bolted on an IBC tank, controlling 230V/380V heating equipment on that tank. Few KW goes here. The tanks can carry anything from milk, to paints, fuels, chemicals. Anything liquid that would need heating. We made a GPS tracker, and we connect a 3rd party heating controller to the cloud. It needs new wiring, 230V and low voltage. Setting the tank on fire is very very unlikely, but even so, I wouldnt take any chances. Even simple things, like missing ferrules, or having insufficient isolation thickness on a cable.
We are not going to do these installations/modifications. So there is the problem, that we dont even have the expertise to make electrical drawings. The engineers here, we make PCBs, not electrical boxes. We dont even know, which standard to bring up. And management's mentality is: If the client havent asked for a standard, it is not required.
Who will be performing installations of this box on the customer side? I bet it typically be a qualified electrician who may flag the design/drawings as not compliant to the Electric Code of the country of installation. This situation is just begging for troubles for your company and may expose to liabilities.
Yes, it would probably just stop there, and bounce back as a problem.
Are you even legally allowed to design such systems? Academic qualifications alone don't make you eligible to certify, design or even work on all kinds of electrical stuff. So maybe design the wiring diagram to your best knowledge to make your boss happy, and then tell him that someone with the appropriate qualifications needs to take it from there.
Probably not. But then again, if someone would ask you, which standard you need to apply when designing a suspension bridge, what would you say?
P.S. Worked with an ATEX approved product where the Ph.D engineer ran a power cable inside a 4,000L gasoline tank 
My first reaction is also that. But inside the tank is Zone 0, so if the current/voltage/power on that cable is below the IIC limits, and the cable can handle that environment continuously forever, and the connections have triple safety, that could be a valid design. In any case, if it is possible to avoid, I would do anything to avoid that.
Anybody can be an "engineering manager".
Dont even get me started on that.