Some magic to remount /system
According to this thread, your device is rootable using framaroot.

As you only need a temproot, the first thing to try would be to:


extract the temproot binary used by framaroot and push it to /data/local/tmp or any folder where you can set permissions
flag this file as executable then run it

$ chmod 777 filename
$ ./filename

if successful, you have temp root and can remount the system read/write

# mount -o remount,rw /system /system