I figured the first thing you’d say is an oil pump quitting.
Well, there is more opportunity for an oilpump to quit when it is on the engine. It is subject to heat and additional vibration that the pump at the back doesn’t see. There are no benchmark test that show a pump in this manner is more likely to fail. In fact, it will show more reliability for the pump to be mounted far away. For example, tell me the reliability difference before the old Mechanical fuel pumps directly mounted on the engine and the in line fuel pump at the back of the car. It is a better setup because the lines to the pump in the back act as additional surface area which cools the oil as it travels to and from the turbo/pump. The engine no longer sees that hot coked oil that the turbo is draining off.
Sure the extra boost piping may be a concern, but again, the extra surface area negates the need for such a large and costly intercooler. Most will say you don’t even need an intercooler period, however STS offers a couple systems with Intercoolers. You put the turbos at the back and you bias the weight amongst the car a little better. Do I hear perfect or close to perfect 50/50 weight on a FR car? No more nose heavy huge turbo and intercooler when you can have the turbo at the back. Increased benefit when you put twin turbos at the back as opposed to stuffing twin turbos up front.
On top of that, most people don’t even run mufflers when they have a remote mounted turbo setup. Turbos wherever they’re placed are known to baffle the exchaust and reduce the noise from an engines exhaust, but for some reason when the turbo is farther away from the engine, the sound gets quieter and it acts as a better baffle.