No it is not indisputable. Would the Founders have wanted wanted this? I don’t think so.
If the Founders would not have considered Cruz a Natural Born Citizen, then why did the same people who wrote the Constitution include in the very first law concerning citizenship a statement that the children of citizens born outside of the country were "natural born citizens".
I don’t think they’d want Trump to run. I think that Madison, Jefferson, Hamilton, Franklin, and certainly Washington would never want a Reality TV star to be president of the USA, especially when he’s never even held any elected office. Clearly, they’d be very troubled by such a dilettante.
The founders would be begging George III for forgiveness if they knew what we’d be up to. However, I doubt they wanted US citizens to be exempt from being pres. In fact, they wrote that naturalized citizens can be president. Cruz is, so what’s the issue?