A very BAD idea: splitting California's electoral votes before other states
The only way I would support this is if California got together with a bunch of traditionally Republican states (for presidential elections, i.e. Texas) and passed this kind of reform all at the same time, with contingency language to the effect that the by-district electoral vote allotment only happens in California if it happens in these other states, too.
Of course, the Republicans pushing this measure in California are not pushing similar measures in Texas or other "red" states. The Democrats are pushing a similar measure in North Carolina, but it wouldn't balance out the California one because far fewer electoral votes are at stake.
Why not just have direct popular election of the president? Like in a democracy? We could avoid having to amend the Constitution if enough states agreed to give their electoral votes to the winner of the national popular vote. They could specify that this only goes into effect if enough states are also agreeing to apportion their electoral votes this way. Maryland has already done this. I would support such a measure in California.