After downloading the module you posted, I modinfo'ed and md5'd it. I got the same results as you. I have just flashed my system to latest cssu+kernel47 (Gotta have a perfect lean system with no hangovers from broken experimentation!) Anyways I modprobed that mthrfkr and it seemed to run ok. So I copied to /lib/modules/power47 AND /lib/modules/current, crossed my fingers and rebooted. It worked! So I do not know what happened the last time I tried. Thank you for this.
As for the unmount at backcover removal, joerg said he believed it was controlled at a driver level. does somone care to post a link to the omap_hsmmc.ko source?