My first question to you is what are you trying to protect?

It sounds like you are trying to protect your controlling interest in the company. If that is the case you will accomplish the same thing if you have 50% of voting shares or 50% of total shares. You are in the same position either way. It will take both of you to "do" anything with regards to corporate actions.

You obviously will only have half of the ownership though under the scenario you presented. So if you are OK with that I don't think you have much to worry about.