Etresoft's MacFUSE is one (rather good) idea.
You could write scripts that hardcode the remote IP address into scp commands. I use this trick for copying files to a remote system. The files all get put into my remote Download folder, which I then move around as needed when I'm on that remote system. Not exactly the same as what you want, but the concept is similar.
You could get a free dynamic DNS name from a services such as No-IP.com or DynDNS.org, and then you would not need to bother with the IP address. I use these for my home and my Mom's remote location.
You could use ssh to establish a tunnel to the Apple FileSharing (AFP) port 548 so you can mount the remote file system. I do this when connecting to my Mom's system. I've scripted the task so I do not need to manually type in the long ssh command (ssh -L 12345:localhost:548 remote.system.address). Then Finder -> Go -> Connect to server -> afp://localhost:12345, where the 12345 is the local port number of the ssh tunnel that leads to the remote system's AFP port 548.
The ssh tunnels also all screen sharing (port 5900) over secure ssh connection (ssh -L 54321:localhost:5900 remote.system.address and using vnc://localhost:54321 to connect, where 54321 is the local side of the ssh tunnel that leads to the remote VNC port 5900).
You could use a services such as TeamViewer.com that allows file transfer along with screen sharing.
There are others, some free, so fee based, that offer similar services.
Message was edited by: BobHarris