A donut shop owner ( a TRUE small business) with 3 employees would have a hard time doubling salaries since their end product is a small-sale-price item. They cannot sell-more donuts to counter the cost because most have a pretty static clientele, and fixed expenses like rent, power, water etc. The additional labor cost would probably come directly from the owner's profit and eventually they would probably just close up.
The problem we have always had is the definition of what IS a small business, and to which businesses the federal income requirement should apply.
If fast food places were not franchises, but owned & operated by the companies whose logos are plastered on everything in sight, a dramatic wage increase requirement would be truly meaningful. The "art" of franchising created millions of "small businesses" that have suppressed wages for as long as they have existed. It was no biggie in good times because those jobs were made for teens who needed a first job. Those types of jobs have more recently morphed into jobs for non-teens, as a way of trying to sustain families.
True Mom & Pop businesses can NEVER compete with the deep pockets of corporate america. The secret to the problem is in redefining the strata and subsidizing ONLY the true small businesses (fewer than 10 employees), with a sliding scale as the employee population increases...and a total elimination of ANY subsidies for any company of over 100 employees. That is a big business.. If you write 100 paychecks a week, you are not running a small business. The mega-businesses should be willing and able to pony up more taxes, since they have pretty much corned the market.