Help Building a City Wide VPN

So normally , clients would connect to the VPN like this:

but what i want is :

Why I want this ?

- Because NIC1 is a city wide intranet connection . There is no internet .Hence to access websites, NIC2 has to be used.But i want my clients to connect through NIC1 ( eth0 ) and to get the public ip of NIC2. ( NIC2 is WAN )

My Questions are :

Is this possible?

My estimated clients are 50 maximum at a time ( pptp and 40-50KBps internet each) . Which hardware should I buy for my setup? ( ubiquity ones ) .

Thank You