I think that's a great idea. Being an ex-performer and now an Events Manager, I would love the chance to attend such an event. It would be great to get all entertainment in one place where they can show off their talent to a number of people and not just one company who may not even use them!
At the moment I am looking for some good entertainment to add to my books and personally, it would be much easier to go to one place and see an array of performers / entertainers. It saves a lot of time and energy for Performers and Events Managers alike.
I would be interested to see how you would plan on putting it together? I mean, would you imagine it being one big stage showcase? or like a massive venue that can hold 3 stages with 3 different variety shows at various times throughout the day?