Seems like here's the answer and solution: http://forum.xda-developers.com/showthread.php?t=2718760 .
Since Android 4.2 and the intro of multiusers there is a problem with bind folders across sdcards, making any attempt on mount bind folders as root would result in visible to root only.
Solution is to fool Android with temporary hijack debuggerd to create the mount binds for us. Thanks Chainfire for this workaround!
* Download both files and rename without .txt
* edit debuggerd.mnt to suit your needs (using any other dir then /emulated/legacy/ will result in read only if browsing folders from sdcard0)
* move debuggerd.mnt to /system/bin
* move mount.sh to any place with execute permissions
* execute mount.sh with any preferred method.
Content of "debuggerd.mnt.txt" below.
# Mount sd hack
mount -o bind /storage/sdcard1/Download /storage/emulated/legacy/Download
mount -o bind /storage/sdcard1/Ebooks /storage/emulated/legacy/eBooks
mount -o bind /storage/sdcard1/Pictures /storage/emulated/legacy/DCIM
mount -o bind /storage/sdcard1/Pictures /storage/emulated/legacy/Pictures
And below content of "mount.sh.txt".
# Mount hack
mount -o remount,rw /system
mv /system/bin/debuggerd /system/bin/debuggerd.bak
mv /system/bin/debuggerd.mnt /system/bin/debuggerd
mv /system/bin/debuggerd /system/bin/debuggerd.mnt
mv /system/bin/debuggerd.bak /system/bin/debuggerd
mount -o remount,ro /system
echo "Mount hack enabled"