One thing Zeta got (about) right, was support for modern media keyboards.
It has become almost impossible to buy keyboards without at least some extra keys for direct access to volume, applications like mail or messaging, etc. Zeta had the possibility to capture about any keystroke, and assign an action, command or folder to it. It had quite a simple interface too, only 2 colums: one showing the keystroke, the other what you wanted to have this do. This second column was drag and drop enabled, so you could just drop an application or folder on it.
This would be something very useful for Haiku to have. Store the resulting config file as text if possible so they can be easily swapped and made.