First of all, thank you for your support 
I have modified my image adding all the IP address, let me know if you need more info.
I’ll try to better explain my needs:
Every device I build has inside a GL-MT300N-V2 with its own OpenVPN client certificate and it’s unique IP address (I have written a series of IP address in the image only to explain), we can user 10.210.0.11 as an example.
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If a user connects to the OpenVPN server and types the GL-MT300N-V2 VPN IP address, it must be forwarded to the web interface into the IP address of the device connected to the GL-MT300N-V2 LAN port.
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If a user tries to connect to the GL-MT300N-V2 inside the home network (typing the GL-MT300N-V2 IP Address, it must be forwarded to the web interface into the IP address of the device connected to the GL-MT300N-V2 LAN port.
Only the system administrator can access to the GL-MT300N-V2 with ssh or thought the GL-MT300N-V2 WiFi port and use the GL-MT300N-V2 admin web interface.
Thank you