If you were to create an electromagnet out of aluminum (say by winding a wire of it around a pencil to create a solenoid), and ran an electric current through it, would an allomancer be able to push on it? The aluminum is allomatically inert, but if allomancy is piggy-backing on magnetism, it should still be able to act upon the object. Especially if we consider one of Wax's force bubbles that have no specific target, so it wouldn't need to "target" the aluminum.