I actually did something similar to this for slightly different use case. I needed to connect to two different VPNs simultaneously that had overlapping cidr ran

I actually did something similar to this for slightly different use case. I needed to connect to two different VPNs simultaneously that had overlapping cidr ranges. So I created a network namespace for one of them, and used that for any connections that needed that VPN, and used the root network namespace for the other VPN. I did have to create two separate browser profiles though, since both firefox and chrome won't let you run multiple instances of the same profile simultaneously.