Wow, this is fantastic, thanks! I was looking for something like this a while ago and the closest I could find was transocks, which is Linux-only, not overly stable, not actively maintained, and TCP-only.
sshuttle is currently TCP-only i remember seeing some people discussing about UDP, and DNS forwarding on top of sshuttle but it hasn't gotten very far.
Forward transparently your traffic using iptables. So, if you use sshuttle on your gateway all the tcps connections to the specified subnets are forwarded using ssh for the gateway and all the machines using that gateway.
sshuttle is a transparent proxy server that works as a poor man's VPN. Forwards over ssh. Doesn't require admin access. Works with Linux and MacOS.
Avery Pennarun is a Hero :)