Does the camera snapping back to first person when you release the Alt key bug you? Do you instead want to leave the camera where it is? And perhaps click on another entity to continue your alt-camming?
The following modified version of inspect.js leaves the camera where it is, until you press Esc:
This modified version of inspect.js is included in the following modified version of defaultScripts.js:
Along with other scripts as specified on the following Web page: