I often wonder why there are so many separate hotel programs and no hotel alliances... If there was a hotel alliance that included enough hotels around the world and allowed earning from all included brands, they would probably win big in the market.
There should be something in the big brands that should meet yout needs:
Marriott offers 30 hotel brands across 5700+ locations in more than 110 countries.
Hilton offers 14 brands across 4,900 properties comprising over 800,000 rooms in 104 countries and territories.
Hyatt offers 13 brands across 698 properties in 56 countries.