2nd: I think there should anly be a Magnetable label for those elements in the wiki, not in the actual game. It may add too much in the description of the elements.
3rd: You're right about INSL should block the magnetic attraction, even if there is a magnetable element across. That should be the only exception.
4th: It doesn't need a free space in a wall for the attraction or repelling forces to go through.
5th: If such a situation would exist, it would be the user's fault for the lag. Just like there's lag in explosions yet people still like to create them.
I wouldn't really support that, but it may work.
I guess the only way really is just breaking the metals.
Here is a new list of things that should be magnetable:
-BRMT
-BREL
-MERC
-Any other suggestions?