good news... we've unlock bootloader now, so it's easy to get root for a1-810 now.
the remount issue still there (it's in kernel), we still need the source to fix it (someone said Acer will release it in 2 weeks).
for unlock bootloader... we can just remove the limitation in kernel, then create a new boot.img to solve it (we don't need workaround anymore).
if you don't like to unlock your bootloader, still can try create a kernel module to do the remount job.