You can leverage a NAS as storage (e.g. using Altiris, run commands on clients against files on the NAS), but Altiris cannot use it as a package source.  You would need to nominate a package server at the site (even a Windows XP/Windows 7 computer can work for very small sites) or nominate no package servers and allow the data to transfer across the WAN.

It can't be used as a package server because it has no OS and therefore cannot receive the Symantec Management Agent.

I would simplify the solution a bit and not use package servers at all.  Assign bandwidth throttling using targeted agent policies, or prioritize traffic at the network level to throttle and prioritize bandwidth usage.  This is entirely acceptable for sites with 1-10 systems, and can even work for larger (1-25) sites.

bandwidth throttling with targeted agent policy - sounds like a good idea...do you have any document (off the hand) that can help me achieve this? - also, as these remote offices of mine have limited bandwidth - would a bandwidth throttle policy help achieve 100% compliance in terms of package delivery, patch deploy, virus def downloads etc....will it prioritze? as currently the bandwidth in these office just gets choked or the latency is so much that nothing gets delivered right!...

You should set it to a certain Kb/s based on the number of clients, size of pipe, availability of pipe.  This is done within the Targeted Agent Settings policy for the Symantec Management Agent.