The answer by Dr Poudel has many excellent elements to consider. Security is another. Amenities include not only very scenic, but also things like drinking water, sanitary facilities for visitors, parking, public transit, food if desired, etc. In exceptional instances of scenic beauty, public need and economic potential, the project may make money and be self sustaining.
But here is perhaps an unconventional idea. There is a contracting approach sometimes used that requires interested bidders to develop a "Proposal" plan of action so they may be awarded the contract and work. The bidders would be competing with others and their plans for development and perhaps management as you request. You don't necessarily have to choose any of the bidders if their plans are not suitable. Your prospectus for proposals should include your goals of sustainable ecotourism that addresses any restoration needs, educational and informational facilities, suitable access that conserves resources such as boardwalks in wetland areas for some fishing, scenic access, ecological walks, etc. Essentially this process allows any interested Company or engineering firm to come up with competitive plans and ideas for development. Incentives if known might be of various types such as reduced taxes or access to adjacent lands for development. The plus in this process is the ability to get varied views and intensities of development, economic costs and benefits, etc. Part of the proposals may include on a separate line item the development of what is equivalent to an Environmental Impact Statement that looks into or studies the effects of the various plans (alternatives) for the decision maker to consider, including the potential of the various alternatives for local community and biological impacts or damage to the wetland functions.
Any up front advice you can offer to those submitting proposals of what you would not accept may be helpful to them so they are not wasting their time in proposing something that is not desired, for instance you might want development be small and consistent with local rural setting and community lifestyle and beliefs, and want to avoid proposals for developing this as part of an adjacent Disney entertainment theme park with millions of annual users.