Actually, a N/A Detroit 2 stroke still has a blower... They will NOT run without it.
Yes, on a Detroit the blower is not a supercharger, it's a scavenge blower.
The higher rated Detroits utilize a "bypass blower" because the blower is positive displacement and impedes the turbo at higher rpm. This is seen as a higher pressure between the turbo and blower than in the airbox. Thus a pressure sensitive bypass is in place to allow air pressurized by the turbo to go around the blower which at that point is inhibiting the flow.
A centrifugal supercharger is not positive displacement so may not require a bypass around it unless the turbo is pushing alot more air than the super can move.
I think you'd be best off to setup and size the two units like a compound turbo system with the super taking place of the small turbo.
Ken
