I'm starting a new project that consist in every game made for the Xbox inside a single HD.
Now days a 2TB sata HD is cheap and this size can store every xbox game ever made.

I was searching for some possibility to use a xbox controller port -> usb adapter and use an external usb bay for the HD.
One other option might be a RJ45 to usb adapter. Not sure if one of those would work.

I have a softmod xbox with unleash X + Ndure (80gb HD inside).

If anyone ever tried that and had success I would like to know.

Won't work and would be horribly slow if it did. (USB 1.1)

What about RJ45 to usb?

Or is it possible to load games via Lan? maybe a samba or nfs share?

one more option might be a 3TB HD via sata - ide adapter. a Hd that huge might work?

No.
Biggest hdd I think you can install with tools available is 2 tb. If you want more you have to have a switch to choose which hdd you want before power on.