This strategy is fine as long as we keep the house but what if we don't? Then it's too late. It's fine to be confident in keeping the house but the President needs cover in case we don't. Do you really want to risk it all on these midterms? Because if the President does not fire Sessions and Rosenstein and we lose the Midterms his entire presidency is going to be over. If he gets rid of them before and can get an acting AG that can put prosecutorial heat on the deep state the President could survive until 2020 then start over. If the President remains on defense and we lose the house it's over.
The problem is -you’re right, we have to keep the House, but, to keep the House the People have to vote for actual, living Republican candidates - and if there’s one thing the People hate worse than Democrats, it’s Republicans.
To understand the chess aspects of this, you have to have at least a small amount of ability to reason abstractly, which only applies to about 15% of the population (if that), which is the whole problem with the voting thing to begin with.
Once the Senate went to the idiots voting method to fill seats in 1916, we were screwed.