The thing is and this is what I find, whilst I can and have done writing rp's with groups of people, there will always be certain characters you just are better able to work with. 
Others might not get the amount of depth or 'more content' that those you click with might have. 
That said, I don't mind having more people, should you wish to bring someone in, but I myself wasn't particularly thinking of it. I kind of gotten used to us three doing Broken Skies, which now had become the both of us. 

Oh and don't worry too much about Eilis, while I enjoy throwing her around like a little ragdoll and tell you her death is imminent, I still need her alive, unless you're going to go rogue on me and suddenly reveal that Arn was an evil overlord all this time, she isn't going anywhere.
Arn's stuck with her.