Sandbox and symbolic links

[Rip]

Please can you cast your eye over this strategy, Dave?

Current:

iMac with internal 2Tb drive. No partitions.
External 2TB firewire drive with SD backup img.
Apple Timecapsule Timemachine backup of iMacHD. Hourly.

Proposed:

Erase and partition iMac internal 2Tb drive then restore from External 2TB firewire drive SD backup img to achieve the following:

iMac with 2Tb internal drive. 2partitions: iMacHD and Sandbox.
External 2Tb firewire drive with SD Smart Update img of both iMac partions. Daily.
Additional External 2Tb firewire drive with SD img of iMacHD. Monthly.
Apple Timecapsule Timemachine backup of iMacHD. Hourly.

Is this a sound strategy, overly complex, redundant in some way?