So there was a bug in the script I uploaded. Apparently it can use the mscompression library with x64, however the calling method is probably slightly wrong, which leads it to crash with x86. Anyways, the bug in the script even prevented x64 to work. Either way, the Jeff's bmzip loads the library as expected, and thus works on both x64/x86. So forget about the script uploaded yesterday. I just recompiled and successfully testet his clean source from github. The test was on bootmgr version 6.3.9600.16415.
Let me know if there's still anything of significance that is unresolved regarding this file.