12 and under is fine, nothing wrong with that, but I do feel they should separate the 13+ section into 4 groups. 13-16, 17-21, 22-35, and over 35s. There is a distinct difference between the groups in thinking and ability, and for the older people it just makes sense as well as they have reduced reaction times but typically greater tactical ability/patience. If Nintendo really developed this right they would have a major success and garner huge support and interest. This in turn would cause major gains in sales and in turn profitability, which would in turn generate more interest from developers, etc, etc....
Especially developing a bracket for older people, this is the age group that grew up with Nintendo and as such would likely increase the number of people playing in that age group, which most have disposable income, which they would spend on themselves and their games as well as grooming their children into the Nintendoverse. Just my thought.