Whatever Brinkster is rejected my attempts to access your diagrams.
Offhand, it would appear that you perhaps should consider a hosted CRM solution and a host email solution and exploit the Internet as your network fabric.
Although one cannot generalize across ten unnamed countries, there are usually plenty of >56 kbs access options, whether fized line or, increasingly, mobile.
The spyware, etc. matters can be addresed in part by adding security applications to the client devices and perhaps by changing user behavior. Also, for PC’s, VMware or other virtual machine options make it easier to set up “corporate” virtual machines on remote PCs.