Ask HN: Marketplace for Rapid App Development? Hackathon Marketplace

As a business owner and digital marketing consultant for larger brands. I get tasked with fleshing out concepts for apps regularly. By the time I get wireframes done and specs done usually the original motivation has passed. My question is this. Is it possible to create a marketplace around hackathon type rapid app development. I could see brands spending upwards of $2k an up for an app concept to be done in 24-48 hours. Would it be worth it to developers to make money in short bursts like this? Anywho.. just a thought .. Interested in your thoughts. Tom