have you seen Ungaze's Interactive Data2sd post on XDA forum? A few days ago I was pm'ing back & forth with Ungaze about porting his tweak over to our phone. He might be a good resource.
Yea, I'm working on a script to move everything on /data to the SD card, /cache partition as well. I know there's a blue million such scripts, I just wanted to tinker with it for my own edification because I like programming..heh.
Storing to RAM is something I've seen a while ago and considered too. It would be nice if the phone called a proper shutdown script and allowed for proper unmounting. Along with that, it would allow saving of the cache area to storage and then upon boot you populate the dalvik-cache in RAM from the saved version.