Dave is correct and I think Da'lan or whatever is the only option.
Things to keep in mind: you will be drilling a number of holes, you will need to be very mindful of tongue weight (I wouldn't even use a hitch style bicycle rack as I think it would tear out), and rear suspension health/spring rate.
I was going to do it for my last E30- 325is- to tow the track bike, but ended up getting out of going to the track very often, sold the 325 and got very heavily into beemers (and obviously out of bimmers).
We got a Da'lan hitch for my wife's E46 325xi, but I never got to install it prior to leaving for Germany, so that will most likely be done when we get home.
Anyway, I don't think there would be a problem if you are careful and don't go over a few hundred lbs. like you mentioned. I think I remember that you are a mechanic, so you already know this, but for someone searching, make sure the brakes are in EXCEPTIONAL working order, and that you have fresh synthetic fluids in the tranny and diff, and that your cooling system is up to snuff.
People tow all the time with very unconventional vehicles over here; I even saw a 993 track car on a full trailer being towed with an S Class Mercedes. There are NO trucks over here, but EVERYONE has a trailer.