Networking: NAT two interfaces together on Windows

I have the following setup:

• Openvpn client (Linux) (Openvpn IP 192.168.99.4)
• Openvpn client (Windows) (Openvpn IP 192.168.99.2)
• Openvpn server (Linux) (Openvpn IP 192.168.99.1)

Now, both clients connect to the server. From the Linux client, I want to be able to access the subnet of the ethernet interface (10.137.137.0/24) of the Windows client. This subnet has a number of other devices on it.

This is what I managed to get so far:

From the Linux client, I am able to ping the windows client on the other interface by adding another route:

sudo ip route add 10.137.137.0/24 via 192.168.99.2

Unfortunately, I am only able to ping the Windows client 10.137.137.1, not other devices on that subnet (e.g., 10.137.137.2).

I want to be able to do this.

Some further info: here is the client-specific openvpn configuration for my windows client:

iroute 10.137.137.0 255.255.255.0

Furthermore, I have enabled IP forwarding on the Windows machine in regedit.

I know that this post is very similar to this one, but I cannot configure Routing and Remote Access on my machine (as shown in the answer), as the option is simply not there in the admin tools.

Moreover, I know I can manually add a route on 10.137.137.2 to route requests from the OpenVPN interface to 10.137.137.1, but this does not scale well in a large network.

I managed to get it working by enabling Internet Connection Sharing (ICS) on the ethernet interface, sharing it with the OpenVPN interface. Finally, I restored the IP address of the OpenVPN interface, as Windows changed it in the process of enabling ICS.