Your strategy would not result in a purely conservative GOP caucus. It would result in a smaller GOP caucus. The people would lose wouldn't necessarily be the RINOs. It would be some RINOs and some conservatives -- in each case, the ones with difficult districts.
It wasn't a strategy, it was a question of which of two alternatives would be better. As to whether either of them could ever become reality, and if so how, that's another issue.
I would posit that in most races, the politicians don't run terribly far apart on the issues (Obama v. Keyes being an obvious exception, but that race was just plain goofy). In most races, if a candidate runs toward his side, the other candidate will run toward him to fill in the gap. One major effect of this that when Democrats run toward the left, they often end up putting in office a Republican who's further left on the issues than would be any Democrat that could actually win election.
Republicans need to learn what they stand for and actually start standing up for it. "Moderate" positions on many issues are actually the least justifiable. Suppose the Democrats want some new XYZ program, with a cost of $20 billion dollars. Would it better for Republicans to agree to spend $10 billion on the program, or would it be better for them to unsuccessfully try to oppose it, with the effect that it gets $20 billion?
I would argue that the latter course of action is better. If Republicans make clear their 100% opposition to the program from the outset, then when it turns out to be an expensive waste of money they will be able to say that its failure was entirely predictable and the program should be killed. By contrast, if the Republicans agree to spend $10 billion on the program and it fails, they can no longer argue that it was a fundamentally bad idea (since that would mean they knowingly agreed to waste $10b) Worse, the Democrats will be able to claim the program failed because it was underfunded and it should therefore receive $25 billion.