I'd have to go double-check my '02 outside, but I believe the steering is from the backside of the strut, not at the front. That would make it pretty difficult to relocate everything. I am not sure if you can just swap the left and right strut and run them backwards either... never tryed.
It would be harder to fit an e30 diff in a '02 than a e36 diff IMHO. The e36 diff has two ears on the back to mount to the frame in a similar fashion as per the '02, while the e30 only has one, and its offset to the left.
I only mentioned the fuel cell as an idea, so you could have a bigger tank to fill to offset the weight. Your stock tank should be more than adequate though. Agreed on the stereo, that stuff adds up quick!
I just put my '02 back on wheels today actually. So good to see it back on the ground on wheels+tires.