As with CBQ and HTB, you will need to make some modifications and patch your IPCOP in order for this to work. I have not personally used it but from the info pages it seems that it will definitely do the job.
The situation is this. You will not be able to achieve what you want without making modifications to your IPCOP's kernel and/or installing additional programs. This in itself could create unknown security risks.
However, I will keep on looking for a solution and if you find anything please post back to the thread as I am interested to see how you get on.
CPU: Pentium III and upwards
HD: 2 GB - no web-caching, 5GB and upwards if you're using web-caching
RAM: 256 MB and upwards
The above is very generous for IPCOP. For example, I installed it on a 486DX2 50 with 32MB of RAM and a 600MB hard disk, and it ran perfectly. The hardware only showed its age whenever I used the Web Admin features.
I think you will most likely encounter problems with bandwidth before you hit any software/hardware limitations.