Several issues with your plan:
1) Rents are high in any good location that people will want to visit. Doesn't matter if it's in a retail shopping center or professional/medical complex.
2) Franchisees are far more interested in a winning concept than saving $25K on an initial franchise fee. The added fee may also be necessary to get the corporate support for a new location. There's a lot that goes into it & you need high-caliber people to advise you.
3) Discount massage franchises cannot afford to pay 50% commission on a massage. To illustrate: $80 massage - $40 to therapist = $40 for the spa to pay bills. That works. A $50 massage - $25 to therapist = $25 to pay bills. That is NOT enough & most spas will go broke. So, $50 massage - $18 to therapist = $32 to pay bills. That works if the spa is keeping their rooms full. I know it's hard to imagine running a spa can cost that much, but the expenses add up fast. Also factor in 20% for fair owner profit.
4) Forming a labor union may actually be viable in some states with new "joint-employer" rule. But doing so will kill jobs. Higher wages = higher fees to customers = less customers = spas going broke = therapists out of work.
Massage Envy & copy-cat programs have delivered massages to the masses. Demand for therapists has risen about 20% in the past 10 years, and is expected to rise over 20% in the next decade. I own a medical establishment with massage therapists. Ten years ago, I could hire them all day long for $12/hour. Thanks to Massage Envy, they are harder to find & I need to pay more. They are growing the industry and creating jobs by the thousands.
If you are unhappy with your pay, quit your job. Real simple. If nobody will pay you "what you're worth," perhaps your services aren't worth as much as you hoped.