Hi Mathew,
I know it is not proper design, But this is how the current process works in 3.x and the client wants to reproduce the same using in 7.X. We are planning to use TVARVC for this. Each and every process chain will set what data it is getting in TVARVC and depending on that the code in transformation will read it and process the data accordingly. This model is being is used to reduce the number of objects(transformation) developed in the system.
Regards,
Raghavendra.