1) Of course Republicans should nominate/confirm a conservative. 2) Of course they can do better than Kavanaugh. 1+2 strikes me as obvious, but I'm clearly in the minority.
But you're basing what should be done now on your conviction about an uncertain future. Prediction that SCOTUS legitimacy would be damaged by Kavanaugh, but not by other conservative noms, is safe. Prediction that Dems will accuse every future nominee of sexual assault isn't.