JeOS (Just Enough Operating System) seems like a good pattern for implementing an OS on Epiphany. If you think it's not possible to make a complete OS in 32KB, meet which is a full OS for x86_64 that fits in 8KB. Assembly is the way to go for an OS of this small size.
However, to make this work properly, the Epiphany must be able to run independently. this means making a modified FPGA bitstream that will enable the Epiphany to work as such. i've but i suspect it will go on ignored.