Hmmm? Just a weird thought...don't move forward with it quite yet, but I wonder if you could cut the nib off the end of cable, melt a hole through that plastic piece and somehow bend/tie/crimp the cable through that rotating piece? Or, if it's plastic as you say (IDK) then maybe you could heat weld plastic back onto it to hold the nib in place?
If you cut the cable, though, you need to make sure that there's enough play for the cable to be in the correct position...and I'm really not sure about that at all. I know that you have some adjustment, but you might not have enough...it'd be tight...and actually, I think that idea of mine might not be such a good one...it happens! LOL
Your tb is probably toast, but given that, a little bit of experimentation isn't going to hurt you too bad. I bet you could find a working junk yard part for around $100 or so. Hey, wait, iirc, Mango is selling one--see E46Mango and his sig file...iirc, he's selling his for $80.
I'm so depressed. No one wants to come see me. :(
Mangofy your E46!