Getting access to a VM inside a NAT'ed home network is going to be challenging. While you could, run a VPN in the VM direct to the internet, then remote desktop to that public IP, that's not exactly a safe thing to do (and you'd have to run dydns or something similar to be able to find where it's connected).
Another option would be the reverse - VPN from your mobile computer to something inside your network (that's behind firewalls/secure authentication solutions - business/enterprise quality, not consumer grade). Then if you use bridged networking for Fusion, your VM will have it's own LAN Ip and you can connect to that.
But...why not just run the VM on your remote machine?