If you manage to fix ED-E in Primm, you can use it as a mull. I'm not sure what the upper limit is for it holding stuff, but it seems to be over 200.
Heh, I had to "sell out" to fix ED-E. I had just leveled and had to dump 15 of my 16 points into repair just to get within 20 of the requirement. A skill book and a feat that doubles the skill book finally got me to 65 Repair to fix ED-E. My ED-E has a carry load of 210 lbs which is exactly the same as me so maybe he just scales to match the player?
Tried to get ED-E to the (optional) quest of his to return him to some junkyard but its far away and it seems to take forever to travel by foot. Tried taking out the prison but walked into the admin building, which is infested with Power Gangers, and in a spastic fit tried to exit the building with one HP. This caused an auto save right outside the building and when everyone ran out after me, a loop of death, autoload, death, autoload... Had to go all the way back to a save in Primm.