Did you consider going the appliance route? Leasing commodity boxes that can mount network shares via Samba or NFS and reselling them as CPE seems like it would work for this particular software.

That way you would control the software load and be able to manage the quality of the product. And you could use a PPA to manage updates etc.

I'd be really interested to know if you considered this but did not do it and would like to hear the obstacles.