This pure speculation. Isn't it unconstitutional for the Armed Forces to be used for simple law enforcement? Are state guards different? How would the state have the grounds to get warrants for every possible household? Next, couldn't President Trump nationalize the Guard and order them to stand down? I recall similar things during Civil Rights days when governors threatened to use the Guard to oppose desegregation (but I could be wrong on the memory).
I do like the idea of deputizing an entire county, the court cases over that would take forever. The progun forces should cite the resistance by local authorities in the North to Fugitive Slave Acts as precedent.