I've got the idea of a triple/compound turbo setup. A very future goal, but a unique one. A larger turbo sitting up front that feeds the twins in a compound setup. I'm no turbo guru, so where are my weaknesses in my theory? And how can the wastegates be sync'd correctly as I'm sure some electronic controller will be needed.
Intake: Filter > large turbo > fmic > Y pipe to twins > smic > intake
Exhaust: this would be tricky. I'm guessing the larger would still be before the twins in the exhaust flow? Or could you go in place of the current down pipes instead to a Y pipe that feeds the exhaust side flange of the larger turbo, then it's exhaust goes to the muffler? My brain hurts, it's too late
Oil and coolant wouldn't be necessary for the larger turbo as I would use something like the CT3-6767 Billet Triplex turbo which uses sealed ceramic bearings.