There are certainly organizations set up to design and manage covenants. One of the issues with putting a covenant on a property and selling it is that the covenant really has no value unless it's being monitored.
Often when a building is sold, a portion of the proceeds of the sale are set aside to pay for the expertise that would be involved in monitoring changes, reviewing changes, and confirming them over time. Really, even with a covenant, the goal is not to freeze the building in time forever; it's really about management of change. We really promote the sustainable reuse of buildings. Buildings have to change and move with us into the future, but it does require expertise to make sure those changes are made in the most appropriate way.