A $15 minimum wage will be a new expense for restaurants. It will be windfall income for the wait staff.
To be fair in the distribution of the cash flow change, and because both parties have a vested interest in optimal service for the dining pleasure of guests, the distribution of these impacts can be moderated by letting the waiter keep half (more or less) of the tips on top of their increased wage and return the remaining portion to the employer. It will help offset the increased wage expense while letting the waiter collect tips on top of their increased base pay. The employer will want to maintain a good working environment and to encourage guests to continue their habit of tipping.
This will minimize an imposed expense on the employer and permit the waiter to have increased security in take-home pay. The patron will see little change.
I have a better idea. Pay wait staff a better wage. One they can live on and then eliminate tipping. I tip quite well because I know these people live on tips. But there is no reason that wait staff should do anything for tips because some people will not give much of a tip even if the server does back flips for them.
Yes. Pay something like $15 then split the tips. The staff would get a living wage and both staff and employer would be incentivized to give good individual service. Patrons would not have to feel pressured into tipping anything. The tipping custom could fade away, or not.