Now seriously, maybe you can somehow manipulate encoder firmware.
650d uses mvr config. I think FW is just setting the registers. 6D/5d3 encoder may have an image as it seems detached (I just load parameters/config, can't change quality in real time). Looking at registers here would help but they are changed and the old code is still in FW to confuse. Maybe tracing out EKO mode will turn up something.... But these are dedicated chips from TI not generic FPGA or something. Nothing in the references says anything about loading an image.
Only problem is shrinking 4mb 422 data to like 1mb h264/jpeg, etc. Jpeg would already come out at 4:2:2... You can't increase that 422 data quality unless you resize it.
If you're gung ho about cutting a solid package up (heat gun would only take it off the PCB) just dump the FW and look, maybe you'll see something.
650D still has room for improvement... needs flush rate and QP/slice setting. 6D can push out 400Mb/s... that is like 2MB frame size so 2:1 compression. I'm not able to do flush 1 currently, maybe 650D can. That is solid break your card writing.
