Comment by vladvasiliu

I don't know about FortiClient specifically, it's a sorry piece of crap that's more often borken than not.

With openfortivpn, you can usually ignore whatever routes you receive and set up your own. I haven't tried the specific set up you talk about, but I don't see why it wouldn't work. However, you would most likely need to NAT on the machine running the Fortinet client.