We all know that Android install apps in /data/app and app's data in /data/data.
I wonder if is possible to "ask" to the system to install the app in /sdcard instead, or on a custom path there.
I know that this isn't good for security reasons, but having the dex/libs accessible without root would be usefull for creating a (sort-of) sandbox.
I'm talking about normal "apk" apps (not just dex files that can be booted with dalvikvm command).
adb install -s
will tell the system you want to install the application to the sdcard.
However, I'm not sure this is actually what you want. It creates an encrypted container on the sdcard, so it's not actually accessible in the way that you want.
So essentially, no, it's not possible. For exactly the reason you already mentioned (security).