Should the "winner-take-all" flaw of the electoral college become a recurring problem, it would likely cause a. a drop in voter turnout.
b. a rise in voter turnout.
C. more elections to be decided in the House.
d. none of the above.

Firstly there is no Winner take all Flaw in the Electoral College. It is illegal to assign Electors based on the national “Popular Vote” - totally disenfranchises the voters of a state.

But by all means, go to the apportion scheme that Maine and Nebraska follow. We’ll gladly trade 1 Democratic elector in Wyoming, South Carolina, Montana for 20 or so in California, 6 or 7 in Illinois, 3 maybe 4 in New York. Instead of all 55 California electors all going Democratic year after year, the rural and northern areas of the state will get a voice.

Remember all that Red in the county by county Presidential election map of 2016, 2020? The Democrats will lose that overwhelming advantage that LA, Chicago, Portland OR, Boston, Seattle gives them.

formulating the initial idea for the policy

answer is c.