D2:ED already has at least some gamepad support:
pc 360 controller help. Maybe the add-on can improve on that, or add a default profile for common gamepads. Until then, if there are limits in direct support there is software to help map functions;
Xpadder 5.3 is freeware (later versions are shareware) or someone in the topic above mentioned using Pinnacle Game Profiler (shareware), etc.
