It would be a little light for your bikes but I have a little fold up HF utility trailer that only weighs about 300 lbs. It's good for 1000 or 1100 lbs. You should probably go up to the 1800 lb trailer. If you want to do this, the other thing you could do is to put surge brakes on the trailer. That is not hard but adds cost. I would just put hydraulic brakes on because they're easier. Your coupler would change to one that has a hydraulic cylinder in it. The way it works is when you brake the car, the trailer pushes on the hydraulic cylinder which pushes brake fluid to the brakes. You also have to put the backing plates and brakes on the trailer and run the lines. You can buy a kit. Especially if you plan to tow on the highway, I would be thinking of brakes if you want to get up around 2000 lbs. You have plenty of power but would have to watch the temperatures on a long uphill pull. Bimmers also do not seem to be real robust in the rear end. I saw a piece on a M3 who stripped the splines off the axles drag racing. Our rear ends have very little fluid in them which makes me a little concerned about cooling. You have enough hp and torque and weight to pull 2000 lbs. The question would be transmission, possibly clutch, and rear end. And brakes.
What I do is to use my SUV. I had a 3 year old Suzuki Grand Vitara when I bought my 128i vert and just kept it. The bimmer has 50 more hp and 15 more ft. lbs but I tow with the zuk. It has a class 3 hitch and handles my boat well (about 2000 lbs). The bimmer would handle my little utility trailer well but since I have the SUV, I haven't bothered to put a hitch on it. I've towed U-haul's biggest trailer (which has surge brakes) with the zuk moving my daughter and it was fine. But I'd rather not try it with the bimmer.
128i Convertible, MT, Alpine White, Black Top, Taupe Leatherette, Walnut, Sport
Ordered 5/22/09, Completed 6/4/09, At Port 6/9/09, On the Georgia Highway 6/13/09, Ship Arrived Charleston 6/24/09 at 10pm, PCD 7/21/09