I propose we make minimum wage a GS-1. (to look at the federal GS pay scale, go here http://www.opm.gov/policy-data-oversight/pay-leave/salaries-wages/2014/g...)
Benefits that I see with this are:
There is already a system in place for cost of living adjustments of the GS scale so the minimum wage can be more easily tied to inflation.
The GS scale uses a locality adjustment, because living in New York is not the same price as living in Kansas City.
The GS scale incorporates time based raises, so if you work the same job for years you get a little more over time
I know it is not $15/hour, but it is an increase, and it puts things in place for continuous increases.
I feel this is a good compromise that both sides of the issue can support.