So, to make it work, I need to know that I want to connect to
192.104.0.0 and 10.0.0.0 via VPN and 192.174.0.0 via my gateway.
Then, I route 192.104.0.0 and 10.0.0.0 via VPN and let everything else
go to the gateway (the old default route).

Now, is there (windows) software the allows one to view and edit (and
better yet programatically edit) the routing tables in my pc? If so,
what do I go looking for (on google or whatever)? This sounds like a
fun little learning exercise.