That would be ideal, but the people who are already there will never give it up.
And the problem with creating a new party is that it will divide the votes, while the conservatives are all united under the Republican party. Unless they split too. Maybe the non Trumpists can split off and form a more traditional party. But again, they're too afraid to split THEIR votes.
Why not both? It's easier to force your way under and into that tent/coalition with an organized front to do the talking. A political party that has well defined goals and objectives, while speaking for a big group, is bound to be better at working within a broader coalition than what we have now.
A reverse tea-party movement. That could work. We were laughing when the tea party started because it seemingly broke GOP unity, but they managed to shift the Overton window so far to the right that the GOP now is the tea party, and Dems are GOP lite. Reversing that trend is extremely necessary.