Love the idea...but why do you think someone would rather use this than just download a PSD with a lot of elements ?

I think the real value you could be creating is if you're able to get tons of designers giving you their 'infographic themes' for cheap, and then charging for access for the app. However, you'd have to make it more 'general', a lot of the themes seem to be very specific, for example, one is for some kind of data around the US demographics;