I'm honestly not even sure exactly what prevents the con from bringing in some of the guests under demand? Maybe they don't budget for it? But there are other younger, fan-run cons in the GTA that haven't had a problem getting guests that meet fan interest and demands. AN has not for a while been a con one goes to for the guests, but maybe that could change.
For cosplay guests at least, I know that there are some specifications and preferences that eliminate a lot of potentials. I ran into Kaijugal a few weeks ago and she was explaining it to me. From what I understand, and if I'm remembering what she told me right, it's preferred that the cosplayer is Canadian, and that they're willing to do workshops/demos/panels in order to educate and help people learn skills. Expecting to sit at an artist's alley table or autograph table all weekend doesn't cut it. If you don't want to instruct because you're scared of other people becoming talented, ya doin' it wrong. I think that's a great system and completely reasonable expectations of make of your guests who are there for cosplay.