A USB or SPI attached display could provide its own FB driver.
The changes I have made means the foundation supplied LCD panel and the HDMI can now run on different framebuffers at the same time, which they were not able to do before. Also, DPI displays and I think composite (not tried either) - anything that the GPU drives.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Please direct all questions to the forum, I do not do support via PM.