Which would be better: to have Congress made up of 49% liberal Democrats, 25% conservative Republicans, and 26% "Republicans" who felt they need run leftward to be and remain "electable"; or to have a Congress made up of 49% conservative Republicans, 25% liberal Democrats, and 26% "Democrats" who felt they needed to run rightward to be and remain "electable"?
I'd suggest the latter would be much preferable. Unfortunately, what we have is the former.
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.