Many buck-boost converters work by boosting to an intermediate voltage, then bucking to the desired voltage. What if instead, it had a separate buck and boost section in parallel, and switched between the two based on input voltage and desired output voltage.
For example, if the converter is set to 15 volts, and it's being supplied with 12 volts, the buck side would be disabled and the boost side would be boosting the 12 volts to 15 volts. Likewise, if you set it for 5 volts, the boost side would be disabled, and the buck side would drop the voltage to 5 volts.
Could this lead to high efficiency buck-boost converters?