I am not a lawyer, but getting something like this in requires that you have a very strong hand in your negotiation position with potential investors. If you have dozens of investors all competeting to put money into your startup and you don't need the best valuation, then you are in a position to ask for this, otherwise it is just going to be another reason for investors to pass.

Very few startups are in a position to negotiate super-voting shares - it is a bit like a group of teenagers in new punk band worrying about what they are going to do with all the millions they will make when they release their first record.