Well, MelissaArtemis already called Caster, so you'll have to work that out with her, but as far as the system goes, certain attributes would be given for free, such as telepathy and insubstantial. In the show, it was demonstrated that a servant and master team have at least a basic level of telepathy with one another. I would say that as long as your master/servant could reasonably hear you audibly, they could hear you telepathically. At greater distances than that, you can transmit simple images or concepts. However, if you want to take higher ranks in those attributes, go right ahead. For instance, a master or servant trained in mental magecraft would probably have a higher rank in Telepathy. Likewise, an assassin servant would automatically get the undetectable trait applied to all their attacks for free because they're an assassin.
To simplify, because the classes are empty templates that an epic hero fills, each template grants abilities to the epic spirit regardless of what they may or may not have been able to do in life. Epic heroes who had those traits to begin with are often selected for that class as a result.
Also, for future reference, considering the nature of the game, it might not be a good idea to broadcast your servants identities and abilities. If you want to discuss those aspects, PM me.
And Cmpuncle, you're welcome to have the same servant as before, if you want I'll reserve her for you. Otherwise I'll open up that servant slot for the others.