ATPL exams cover areas that are applicable to >5700 ops.
CPL exams are more aimed at <5700 ops.
Its all well and good to know how to load a 727, or how the brayton cycle works in a turbine engine etc but if you are flying pistons a thorough understanding through the CPL course component is more applicable.
Perhaps HF can be a joint exam, IREX covering ATPL airlaw and Met could be a joint exam although I doubt you need sig wx charts and Grid charts in a 152!
back to dreaming, you all know how resistant to change this industry can be!