Get rid of the runflats, I had the Bridgestones which were recalled and the Continentals which I got as part of the recall. Once those were gone I got a set of Michelin non runflats and the difference in ride quality and noise was astonishing.
I don't think a true Limited Slip Differential will be a very likely option since BMW seems very adamant about not letting the regular 3 series encroach upon the M3's territory (makes sense from a business standpoint) but maybe they should consider offering it as a Performance part. I would definitely buy it, plenty of us want to improve the handling of our cars without going all the way to an M car.
Stay true to the traditional interior design philosophy. I'm all for evolution of a good idea, I just hope the feel of the BMW interior remains intact. Sitting inside a BMW after a Mercedes or Audi (my family has plenty of those) to me is like leaving Las Vegas and coming home. One is a place I like to visit on occasion, full of distractions and cheap thrills, the other is a place I live where function takes precedence. I love how easy to read BMW's gauges are, I used to think Volkswagen's bright blue gauges looked cool when my dad had a Passat but then I drove a friend's GTI at night and realized how fatiguing the color is to my eyes.
Any other things I can think of are because I simply bought the wrong car, I was impatient and grabbed the first one I found with a manual transmission (it's a base model, exactly zero options on it) when my driving style and taste in cars means I would have been much happier with the sport package. I should have gotten a coupe too, I have to sit pretty far back so the B-pillar on my sedan blocks most of my visibility out the driver's side
