Sing any song you want to in F, as long as it fits your voice. I think that's the basic message.
I haven't yet been to MLAG, but I'd like to go; perhaps next summer if time and resources permit. I have to confess that right now I just have the one chromatic, in standard setup - a beautiful walnut and spruce Keith Young. At some point, though, I'll get myself a diatonic, and when I do it'll probably emphasize D and G. I'm sure one day I'll have the whole collection.