While Accordance usage is mostly an interactive endeavor, I can think of a couple other ways to involve automated scripts. Or perhaps a global find and replace of terms. With a text file, any desired capability to work with textual data is now possible. With locked UCMs, researchers and scholars could charge for their modules to recover costs. The locked UCM could be neither imported nor exported.
Content control is certainly another reason to allow for locked UCMs.
UCM would be fully compatible with all other Accordance modules. Dr. Brown, when you say fully searchable, this implies searchable just like any of the standard modules that accompany Accordance. This will be great. Some items that would never be published or even considered would suddenly appear. Since text files can be email transferred or downloaded via web pages, the ability to communicate would be easy.