Creating a website for a Tourism BSO, (Business Support Organisation) like hotel associations, tour operator associations follow the same principal as destination marketing and tour operator websites.
The pages should be build with an Inspire, Help, Proof and Sell Principle.
An example of an BSO website is the website of the Caribbean Hotel and Tourism Association.
Though the messaging could be a bit sharper they follow parts of the framework.
See their opening message: Inspire : strengthen your business, which is attached with a Call to Action : Become a Member (Sell)

They explain who they are and what they do (Help) in combination with USPs like, Leading Association, Association of Associations. Again they tie the message up with a CTA - Contact Us.

Help - Overview of the events they organise

Proof - Testimonial - showing CHTA is valuable for their members

With the teams of Kingsfari from Zambia & My Local Passion from Myanmar , VTP digital marketing build and supported various BSO and Tourism Association websites.