Multi-core processors already do this. Give the Android OS a Core or 4, the Linux OS a Core or 4(or however many). The power management already works in the suggested configuration as well: High-power cores are put to sleep when not in use.
The remaining question is whether the hardware virtualization is in place on the specific ARM chip in question to give/confine the one OS(virtualized/parallelized, not dual-booted) a specific Core or set of cores. It could be desirable to give Linux and Android each a low-power core and have them dynamically split the rest, with Linux controlling prioritization.
There are high-powered Linux apps. Moreso than Android in-fact.