To change the way the exhaust flow hit the turbine would mean a new manifold with a different shape to it i.e. short runners, equal length, or long tube.
If you want to reduce lag then go with a short runner setup, for better bottom end go with long tube.
As for modifying the turbo its self good luck! You can go at you turbo with a saw and welder and let me know how that goes, I am sure the guys that make the trubo's are a lot smarter than your buddy