[quote=@Kost Alter]
Whether or not Masters and Servants can inherently communicate telepathically tends to be inconsistent between various Fate works. In Fate RP's, I usually assume they cannot, unless it's specifically stated that they can.

As for magics possessed by OC's that could specifically help in this situation, would Xavier's displacement magecraft be able to work on sound waves? That way Masters could talk to their Servants without shouting and without wasting Command Spells. It sounds kind of iffy though, so what do you think @Moonlit Sonata?

Does he have any support magics? What about his Charisma? Would it boost the party or nah?
[/quote]

Not really? FSN, FZ, Apo, Extraverse, etc all have that connection as being usable. With that said, it's the result of a familiar link, so if you're a total incompetent then you aren't able to use it. 

Try it and find out. 

The stat sheet is all-inclusive. Charisma does not provide parameter increases.