If they are smart, they'll return to being the party of a small, non-interventionist government... Leave the social issues alone, they really aren't the federal government's place anyway. Focus on spending and the deficit. 2020 could be a huge opportunity for the Republicans by ditching Trumpism, which didn't start with Trump. The Democratic Party is a mess and the 2020 election has the potential make it worse, even if they do win the Senate.
i don't think there is much of a market for that brand of conservativism. it doesn't fulfill the policy desires of the majority of current republicans (christian social conservatism, nationalism) and it has been pretty broadly discredited by the empirical evidence of the 2010's where expansionary monetary policy undeniably produced better outcomes than that ideology predicted and tight fiscal policy produced worse.
i think there is more of a market for a sort of powerful state federalist ideology along the lines of what you mention. i think that would be a fundamentally crippled ideology because you divorce the branches of government charged with producing outcomes (state/local) from the branch of government with the capacity to address national challenges (federal). but i think there might be a market for it.
here is a semi-interesting interview with a conservative envisioning channeling nationalist urges into a healthier conservative party than the xenophobic, closed door ethnonationalism of trump. i don't think it's likely to get much traction either, but it's one vision of how a non-abhorrent republican party might rise from the ashes of trumpism.
