SUGGESTIONS WANTED (NETWORKING)

This is very important project so plz read the specs carefully and post your suggestions and the way you`ll follow to complete it , using PMB! we need to develop a system for local bank. Bank has many branches in state. All branches need to report to main office on daily basis regarding total transactions and total input output. We want a robust solution for it ,bcos our job includes setting up hardwares , networking and connection software. We want it to be a robust system bcos if any prob arises in pcs in any branch(like viruses, crash,etc) then we have to drive to perticular area and fix that. so we want extensive suggestions from all professionals. Suggestions regarding system we can use to connect them(there are almost 50 branches to be connected) . What we have in our mind is: 1) Use internet for connecting(but we dont prefer it , bcos then we have to provide internet devices and other setup) 2) RAS server. 3)DOS based Telnet. 4)ISDN etc etc. Our primary goal is that whole system should be: 1) Cost effective 2) Robust 3) VERY VERY PROFESSIONAL(bcos we want all projects like this one to come to us only from our area), no one should get any idea about how this system is working(as far as possible). PLEASE PLEASE DONT AUTOBID , POST YOUR CUSTOM WRITTEN SUGGESTIONS IN PMB(I am not interested in , how much sites you completed b4 etc.) This is huge project and more project like this will follow this one. Thanks and waiting for your suggestions.