No, I am not asking to pretend to be a Rogue Trader without a facsimile of a Warrant. We can produce a falsified parchment easily enough, especiallly as each is unique
The whole point of pretending is so they don't suspect us, because any real investigation will discover that Vita is an AI no matter who we claim to be. Most Imperials do not have the authority to shoot the Rogue Trader just to be sure or deny entry.
Most Imperial officals would check our trade goods, not just a zealous imperial who suspects xenos contraband. Even the corrupt who would accept contraband would check to be sure of not being cheated.
We could pretend to be ad mech, but only Hertek Mechanicus. A non-Imperial ship will need an explaination, and we only have low level codes not anything high enough to be recognised as authorised for independant operation.
A major hacking success is a bit much to gamble on, but if we successfully insert records then that could help back up any pretence from Rogue Trader to Mechanicus. If we are successful at hacking we could probably rebuild our ship (or at least the exterior) to Imperial patterns, and use stolen codes to successfully disguse our ship and Vita as Magos.
"Rogue Traders are too noticeable and too powerful to be good cover unless you have a good grasp of how they work IMO" My objection to Mechanicus is that we don't have a good grasp on how they work at the level of ship captain Magos. Any ship travelling through the Warp is noticeable, and powerful.
Rogue Traders do not follow a set procedure like Mechanicus, there is nothing to get a good grasp on.
There is no such thing as not being suspected by Imperial Authorities, only managing suspicion, which is easier to do with a subculture we can understand like the ad mech than an institution we do not like the Rogue Traders. Keep in mind the Imperium is massive, Tera itself does not have a full accounting of the various types of Imperial hull. As long as we do not have the words 'Xenos Rule, the Emperor Drools' spray-painted on the side of the ship no one will know we are not an 'Imperial Pattern' without being told as much. You are trying to avoid a minor inconsistency, hull type, by claiming to be a sort of ultra-rare noble with rights to trade with xenos.