lol, i never said its a good solution, just the only reasonable one. The best solution is having government controlled public restrooms and regulating where dining institutions can operate their businesses to restrict them to areas where these restrooms are located.

Then have a always on-staff, thats well trained, well payed and lives in the local area. A Government personnel to keep them clean and paid for by tax payers, rather than wait staff that are forced to do it on top of their already demanding jobs of dealing with customers. Treat it as public infrastructure like roads and sewer and the problem solves its self. People generally treat public infrastructure much better than business infrastructure. They see business infrastructure as a outlet to their gripes with a businesses practices. Some one wants to vandalize? its suddenly not a business they are messing with, but a government facility... holds a lot more legal weight and punishment. Additionally staff have only one job, that bathroom facility, so if something happens, they are not going to miss it for 12 hours until some one complains...

Would it be worth if financially? yes. Most governments spend more per year on research groups to make policy decisions than staffing. Staffing costs are generally one of the lowest operation costs, and infrastructure pays for its self when you tax businesses for the use of it. Businesses ultimately save money, as its additional infrastructure they dont need to maintain or clean, and less operational cost.

Will it be done? no lol
Nearly every nation is trying to shift national operational costs to private industry as decades of corporations lobbying and pressuring has made it appear as if its cheaper to build it and sell it to them, then to operate it yourself. People are stupid and easily convinced against their own best interest, because they get situational biased based on the fact bad experiences are heavier than good ones mentally and businesses know how to placate them with sweet words and entertainment... We will own nothing and like it. its the future.