The phrase "as far as it is possible to assume" is often used to denote a certain level of speculation or estimation. There are several synonyms for this phrase that can be used to convey a similar meaning. One option is "to the best of our knowledge," which suggests that the information available is being used to make an educated guess. Another alternative is "presumably," which implies that the assumption is based on some logical conclusion or evidence. A third option is "hypothetically," which indicates that the assumption is being made for the purpose of creating a hypothetical scenario or thought experiment. Each of these synonyms provides a slightly different connotation, but all communicate an assumption made with some level of certainty based on available information.