Looking through the forum links, the main themes that arise are: signatories or witnesses to the Emperor's signing who also lent their names to the document, obligatory purposes as an agent of the Emperor, allowances as an agent of the Emperor, and anachronisms befitting the age of the document (being in the Emperor's own voice, high language, including references to things that don't pertain or exist anymore, current warfare or social prerogatives, etc).
The anachronisms are fluff that make the warrant stand out as ancient, but they could be directly pertinent to the purpose depending on the circumstances in which the warrant was issued and the nature of the trader it was issued to. Raleigh's charter reflects a great free license that one would expect due to a Rogue Trader, but other explorers may have provisions or limits (like the aforementioned reporting to Mars, or the Administratum). Those show a strong tether of oversight, which is a lot more than assigning counsel, as Elizabeth does for Raleigh. That such oversight was needed is telling towards the trust or faith in the recipient!
The Raleigh charter reflects not just his legal ability to act for Elizabeth, but turns him into a protected body, that if injury is done unto him or his heirs, Elizabeth and her heirs will respond to make restitution with "the full Fortes of our realm of England." Raleigh's charter shows not just trust in an individual, or grants of allowances to his heirs, but perpetual relationship as an extension of the monarch, whoever she or he may be. This is a legally binding and honored document. There is no clause for voiding or ending the charter. Consider it from this perspective: Raleigh has a ton of descendants. Those of whom could call themselves heirs could, in theory, call upon the aid of the current Elizabeth (who looks fit to live forever) if they started colonizing Mars and got into an "international incident" like a fist fight with a cosmonaut. It starts out vague to allow for the unknown, then talks about more relevant specifics, like what to do in Newfoundland. A RT charter should be similar. That also means it has interesting potential ramifications if it was left so open; rather than the anachronism of being able to call on the Lunar Wolves, the dictate that "I shall render assistance to fit the need" could be both exciting and dangerous!
Meanwhile, I actually dug through some Drake documents (as in Sir Francis). Unlike Raleigh, Drake was given his initial orders secretly so there was no charter or warrant. In addition, Elizabeth lost Drake's journal on his circumnavigation of the world. The details were kept as state secrets for some time, and scholars were kept in the dark (including Drake's corespondent the cartographer Mercator). Drake was bidden to keep silent lest others discover he had been in Phillip of Spain's territory - Elizabeth put the kibosh on any discussion to keep that one fact out. A charter or warrant could skirt or make references to past actions rendered or future ones promised or tasks and provisions from other long-gone documents; a trusted hound like Sir Francis could carry out secret missions independently, a far different relationship than just-as-trusted Raleigh! Imagine that in the far, far future! The warrant is so sparse because the secrets can't be spilled!
Some orders for the individual (like Raleigh and Newfoundland) may be of a more direct military nature. For an example of text including Elizabethan era orders, take a peek at for language. These are general orders (as well as covering taking in common woman and admonitions not to blaspheme. On that note, so might a RT warrant mention faith or lack thereof - spreading the Imperial Truth), but the Duke and Phillip were in correspondence about Sir Francis Drake and his activities against Spain and the summaries of the Spanish documents are insightful: .
So to sum up, to me, if we want to know what's in the warrant, we need to know more about the first in the line, Arthurus Leahas Isordan Drake, his nature, honor, and trustworthiness, and his relationship to his monarch, the Emperor of Mankind. What the Emperor saw Drake fit for will greatly influence the language, provisions, allowances granted (and perhaps who else was deemed proper witnesses!) in the warrant.