A BlizzVision is not recomended for the desctop as it runs very hot. A heatsink and fan could theoreticly work but the risk of overheating is still there (ofcuase the BV can be underclocked to help). Then there's the question will the USB fit together with the BV... I don't know, probably need a clockport extender.
That said I'm one of those that have expanded the A1200 bewond many others dreams and with a bit of imagination there's plenty of space.
About the BPPC I'm not entierly sure you can fit it to the desctop without adding A) extended feets to lift the system slightly , B) either add holes or a custom trapdoor to help with the airflow.