I am not against using 786, the reader does understand what writer meant by that. We can write s.a.w or a.s rather than writing the whole words, same in this case as long as reader and writer both know what it actually means.
Anyway coming back to alternatives, if someone doesnt find 786 convincing; I do have an alternative for you. My father told me to write :bism: in arabic with my index finger (right hand) before i start the exam. You get the satisfaction of starting the exam with name of the Almighty creator and dont have to worry abt someone droping the paper or other sources of disrepecting Kalam-e-pak.
wasalam
Aqeel