The extra weight of a double body and associated increased fuel costs would totally negate any savings in time.
Not only the extra weight, but the airworthiness must be recertified every time the pod is reattached. After all the mechanical, pneumatic, and electrical connections are made, they must be certified by someone (read criminally liable if there is a screw up), then inspected by a certified inspector (again liability creeps in).
Constant couple/decouple operations will result in wear and maintenance, taking the whole pod and/or flight frame out os service. Maintaining 100% interchangeability among all the pods and flight frames is not an inexpensive endeavorer.
Easier solution is more and bigger entry/exit doors to existing aircraft. Use more than one jetway and board from ground level as well.