The most important route to improvement here is a legal clarification.

You should explain that "joint employer" here covers the structural fundamental of franchising. The issue is whether for purposes of the federal labor law, franchisees are the employers of the people who work in franchised businesses. The traditional rule is the one that follows the intended design of the franchise model from the franchisor's point of view. Where the other forms of legal relationship follow the model (so that for purposes of incorporation, taxation, insurance, and dozens of other legal regimes, the franchisee is an independent business having complex and interwoven contractual relations with the franchisor, unless the franchisor chooses to acquire and operate that business) NLRB in 2015 chose for the first time to pierce the architectural pattern, and use "joint employment" as a concept with reach to reach the franchisor under the NLRA.

This may be ultimately the right decision. It's attractive social policy, for all the reasons you give. The argument is strong that it lies within the statutory powers Congress enacted. But it is hardly surprising that the pushback is substantial, and that with the Republican Party in full control of Congress and the White House, there's legislation. But it can't get enacted in the Senate, for sure, so the matter revolves in the partisan gravitation of the NLRB.

If you give more attention to the legal and political economy context of franchising, the next draft, wherever you bring it out from a policy point of view, will necessarily be in closer touch with the complexities.