Automated Video Slider with Pan/Tilt Head - Requirements

Being a one-man shop I often wish I had an extra pair of hands to control the second camera.  Usually I set such a camera with a wide-angle lens trained at the event audience.  To add life into the footage some panning and sliding are highly desirable.  I am thinking most of the time this task can be fully automated!
Let's call this automated slider with pan/tilt (possibly zoom) head a camera control system.  Or the system for short.

High Level Requirements

• Once setup, the system should be capable of operating fully autonomously, with no operator involvement for at least 2 hours.
• Operator will be able to program the system. The program/script will reside in a separate file which can loaded/saved or created on the fly.
• The script will contain instructions like these:
• Rest 5 secs
• Pan left 20°
• Rest 15 secs
• Slowly pan left and slide left for 5 secs
• Camera control script requirements will be spelled out separately. Including:
• Operations supported include pan/tilt/slide/zoom/rest.  
• It should be possible to run operations in parallel or in sequence or in a loop.
• Operation arguments will be in time units or angle or distance units.  
• Operation with no argument may have qualifier, e.g. fast or slowly.
• Exceptions such as a slider reaching a limit or boundary should be supported.
• System should be scalable in terms of its capabilities.  E.g. it should be possible to use automated slider without automated Pan/Tilt/Zoom head.  And it should be possible to use the automated PTZ head without the slider.  Similarly the script created for a long slider should be usable on a smaller slider.
• System should tolerate power interrupts.  Ideally, once the power is restored, system should continue execution of the script where it was interrupted.
• Power supply should be modular, so that both battery and AC power are supported.

Constraints

• System power supply should be modular, so that both battery and AC power are supported.
• System will be built from the readily available of-the-shelf components.  Integration level of such components should be as high as possible.