The challenges of making a complex GUI accessible include:

1. Balancing complexity and simplicity: Making complex features accessible without oversimplifying them.

2. Providing alternative text: Ensuring all visual elements have descriptive text for screen readers.

3. Keyboard navigation: Enabling users to navigate and interact with the GUI using only a keyboard.

4. Screen reader compatibility: Ensuring the GUI works with different screen readers and versions.

5. Color contrast and visual clarity: Ensuring sufficient color contrast and clear visual hierarchy.

6. Dynamic content and updates: Making dynamic content and updates accessible to screen readers.

7. Custom controls and widgets: Making custom controls and widgets accessible and keyboard-navigable.

8. Third-party component integration: Ensuring integrated third-party components are accessible.

9. Testing and validation: Thoroughly testing and validating accessibility features.

10. Staying up-to-date with guidelines and technologies: Adapting to evolving accessibility standards and technologies.

11. Balancing aesthetics and accessibility: Reconciling design and accessibility requirements.

12. User testing and feedback: Incorporating user feedback and testing with diverse users.

Addressing these challenges requires careful planning, collaboration between designers and developers, and thorough testing to ensure an accessible and usable complex GUI.