For the 3.0Si the stock oil cooler is really a heat exchanger located next to the oil filter cap. It uses engine coolant to stabilize the oil temperature and aids in cold oil warm-up. BMW's in general usually have high oil temps in competition driving. Long hill climbs being one of the worst as there's less cooling air flow. I wouldn't worry about short track auto-Xing but an oil temperature gauge would be nice like on the old Z3 M coupes.
Con-rod bearing stress goes up with the square of rpm so I only briefly visit redline