The winner take all system didn't start till the 19th century when the big city machine bosses started it to enhance the national power of the big city machines. There would still be the two statewide votes for each state under the proposed California system. The big problem is that the US Constitution very explicitly states that the state legislatures determine the method of selecting a state's electors. Even if California's constitution states that referenda passed by the statewide plebecite are officially acts of the legislature, I don't think that satisfies the US Constitution's requirements.
I understand, and I’m not talking about the letter of the law (either the CA constitution or the US) but rather the intent that states, not the population, elect presidents. As someone else stated, it was inconceivable to the Founders that a state as large as CA would wield such electoral power, and be so diverse that virtually one-third of the state would have completely different voting sentiments than the other two-thirds.