The idea of 70/30 or other offset splits only suggests that one partner is more valuable than the other, hence by definition they aren't partners - they are superior and subordinate. You're already creating a situation where the person with lower equity isn't as motivated as the one with more. That has failure written all over it.
I think if you're talking about taking a business from piece of paper to something real, and you have partners involved, the only way you can ensure any measure of success is to divide things equally.
If the share isn't equal, I don't think partnership is what you should be discussing at all.