When using computer in corporation network, I would like to define access to several network areas in the corporate network.

I have following situation. When in corporate network, I use ethernet connection to connect a corporation resources, and mobile broadband to connect internet.
In such a case I must restrict corporate connection to "use only for resources defined in this connection". While I sit in one place, I could define other subnetwork resources in this connection using IP address of the gateway which I receive over dhcp, and it works just fine. But when I move to different location in corpo, then I have to define new connection, because this new place is located in another network segment. 
So when I use corpo network, and broadband internet, while moving over the sit places, I need for each place new network connection definition.

It would be perfect, when on definition of routes in NM there would be an option to select the default gateway, which is received by dhcp. In such a case NM would assign automatically correct gateway for each network segment. Right now there is only possible to set static gw for each additional route.
I could write value "default" for the gw, or leave it empty, and then NM should get default gw for this connection, and use it for this particular route.