Pre-Paid gift codes, great business and community idea.
Mixer many people would love to subscribe to other streamers, but not everyone likes using paypal or debit cards, so, if you were to add gift codes containing money, that people can buy in stores, which they can use to subscribe to people, or buy Mixer Pro, that would be a great way to help people who don't use bank accounts or paypal, because then they could support their favorite streamers, there's a lot of people like that, hope you use this idea :) A bit like Microsoft Xbox Credit Gift Cards they sell in stores, thank you :)
Being able to pay for subs out of the Microsoft wallet through the Xbox Store would be a good option along these lines.
This would actually be pretty easy to implement with Microsoft Gift cards. They're already in stores so they could use those.