VPN between static IP address and dynamic and under NAT IP address

Question

I have to connect two network like that:

RemoteLan<-->Router3G/Firewall<-->INTERNET<-->Firewall<-->LocalLan

So, I need to reach a device inside the RemoteLan from LocalLan. The firewall has a static IP address and also is the VPN server (OpenVPN or IPsec), but the remote 3G router has a dynamic and under NAT IP address. The remote router also is a firewall and can initiate the Open VPN connection.

Is this system technically feasible and can I reach the remote device?

Thanks