That’s why we need to make the GOP cease to be a major party, and replace it with something else.
After all, we’re not still choosing between Federalists and Democratic-Republicans. I haven’t heard who the Whig candidate is this year.
Your not going to be able to organize people to try to destroy the GOP. There are just way MORE movement conservatives and Tea Party folks working within the GOP (particular at the local and state level) to make it more conservative. Your idea isn't realistic and is actually working at cross purposes with many of your own allies.
A US political party implodes when it becomes immovable over some big issue(s) that massive numbers of voters give up on the party over. That is very, very unlikely to happen now or anytime in the foreseeable future. The Republican party platform will be fairly conservative (even though most of us on this forum don't believe or nominee really is at heart).
The 3rd party thing is a waste of time. You'd be far better off spending time explaining to people how to get involved in the Republican party at the local level in their town, city, state. If more conservative activists DID that rather than just TALK about dreams of a 3rd party, we'd be moving even faster towards pushing the GOP to the right. You'd be simply amazed how few people actually take the time to simply register and participate in local party meetings. All it takes is someone to grab some friends, show up, and just that alone can have a LOT of influence. Those are the basic things that need doing. It's fun to chit chat about the grand national level stuff, but that's not where the vast majority of people are ever really going to have an opportunity to make an impact.