Actually, I'm not. My first choice would actually be one of the classics. However, Em was the only one to even suggest a Doctor she might attempt, so I'm hoping to persuade her. :)
River can handle any Doctor, but since Eleven knows her, there's at least a little less angst involved with him. On the flip side, a Doctor that doesn't know her has all kinds of other challenges for her to rise to. I'll take anyone!! Anyone at all, I tell you!!! I'd even take Clara.