Hi,
I'm a skilled and experienced Network/Linux Administrator which is confirmed in my skills. I worked 6 years in ISP as Network Administrator so I know networks, routers, switches, different VPNs perfect. IPSec, OpenVPN, PPTP, PPPoE - whatever you want. I know Cisco, HP, TPlink, Dlink, 3Com, Huawei and other vendors. Regarding to your project, I've read it carefully. My propose is to use e.g. TP-LINK TP-WR740N with DD-WRT - it is very cheap and DD-WRT is much customizable. Then setup on it OpenVPN maybe PPTP. Moreover I advice you, deploying http traffic redirect to VPS - then other e.g. torrent, ftp will go with default on router and only www sites will go through your VPS/Squid. I dont know even if Squid in this situation is necessary - we should talk about that, but I think my propose with split traffic is very good (you will save bandwitdh and performance on VPS). Generally I know routing, firewalls issues perfect, also Squid. I can do this project for you for 300$ - I mean, in this price is: concept of all, deploying Squid + up to 5 routers, documentation, maybe some scripts (if will be need), to automate deploying for future. I'm waiting for contact from you, regards.