Good idea...
I am using the similar method..
First, I replaced the standard bubble level on my EQ6 with more sensitive one. Adjusting the length of the legs is not as easy as with your gadget, though... I wish I found some sort of helical thread for the job.
Also, for (rough) south direction, I am using compass (mounted on 1metre aluminium shaft, so it is away from metallic objects in the mount).
The arm could be attached on the mount in repeatable way.
The first time alignment took some time... the next one (even on different spot) is always easy.