Generic support for arbitrary screen resolutions

One of the nice features of the Raspberry Pi version of RISC OS is that it can support arbitrary resolutions beyond what’s supported by the monitor when mode changes are disabled. As I understand it, this is accomplished by configuring the monitor to use its native resolution and creating a Dispmanx layer in the resolution that RISC OS requests. Given that the necessary functionality seems to be exposed by the overlay API, is this something that could be provided in a generic way for other video drivers with overlay support?