Finally I found out how I can put large libraries (or Garnet VM memor image) onto the MMC and symlinking to it. This can save you lots of device memory.

How to do ?

1. Modify /usr/sbin/mount-mmc by removing 'noexec' and setting fmask to 0033 instead of 0133.
and remount the mmc, e.g. by rebooting or connecting to a PC USB and disconnecting. The files on the mmc should now have attributes "rwx r r".

2. Create a folder with a name whatever you like (e.g. 'overflow') on mmc1 or 2.
3. Move large libraries (e.g. libwebkit) or Garnet VM memory image (~/.gvm/gvm.store 16MB) to that folder
4. Symlink these large files , e.g. the case of Garnet VM image
and the Garnet VM should work normally. The same you can do with large libraries.

You probably won't be able to update libraries which are symlinked to mmc. Didn't test but usually .debs expect that chmod and chown work.