Yes, it's possible to install a BPPC in the trapdoor slot, there is not many other places to install it. The BPPC has a slot for installing a BVisionPPC graphics card, and the BPPC can take 256 MB ram.
The only problem is heat and power issues, as airflow can be difficult to optain in a desktop A1200.
The Shark will most likely never be available, and you need a tower Amiga for that anyway.
As for USB, there is a Subway USB.
