Two differing strategic responses present themselves:
1) Move the GOP further to the Left. Become even more like the Democrats. Maybe we can suck up additional moderate and independent voters!
or
2) Find a candidate who actually believes in Conservative valuies and actually wants to make the case for Conservatism. Sell our ideas to the moderates. Convince them that the Left is wrong. Take a principled stand and educate the voters.
It can be done a number of ways as you outline, but the only way to win in 2016 is convince about 3 million people that voted for Obama in 2012 (and probably in 2008 as well) to vote for the Republican candidate.
It can’t be done by squeezing out 6 million more “true conservatives” to turn out that didn’t vote in 2012 because
1) they don’t exist
and
2) If they did, the vast majority are in states that Romney won easily anyway.