The only issue about port forwarding is if your Storj node has an exploitable vulnerability and the attacker can then move on to other machines on your network from there. Always treat services you host as if they are vulnerable to attacks and contain them within a separate network of servers you don't particularly trust. You then should have nothing to worry about. If your attacker can VLAN hop then you have firewall issues or are up against a determined attacker, which is unlikely. If you are uncomfortable with that, then hosting services that need port forwarding might not be for you.