I'm also not an android developer so take this with a grain of salt.. the mainlining project http://elinux.org/Android_Mainlining_Project has a chart of all Android kernel features which need to be supported.I'm not into Androids inner works so forgive me if the question is stupid, but what about the mechanism/resources that outreach the "simple" functionality of a vm? Wouldn't we need all the filesystem structures, databases, etc. and does this bear possible conflict potential with the Linux distribution used in parallel / as host
Then there is the dalvik vm which needs to be compiled for the system (not a problem).
Then IF there are any standard system libraries which android has modified to be incompatible with the linux ones, these need to be LD_PRELOADed before executing the android app in question.
Not sure how input and sound/video output would be arbitrated. THP's apkenv seems to do it already.
Would help if we had an android dev here to explain more.