But here's my concern, will Ducey replace McCain (assuming the POS will step down) with a conservative or a RINO?
It's hard to tell. A lot of times these guys are not who or what they appear to be. Look at Jeff Flake. He won based on the "fact" everyone thought he represented a hard line conservative platform. He is far from it. He's been all over the map on many issues, health care among them. He's too easily swayed.
That asshole Joe Manchin is another one. He's supposed to be a "conservative Democrat". The NRA was even bull$h!tted into giving him a A+ rating. Remember his supposed "pro gun" stance in that silly commercial, that showed him shooting at a target of Obama, or some such? He flip flopped on gun control right after Sandy Hook. I don't trust his ass any further than I could throw it.
So Ducey could get B.S.'ed politically into appointing someone who could turn out to be nothing but a conservative back stabber, once he or she gets in. We'll have to bite our nails and wait and see. With all that said, I don't see how he could put anyone in there worse than McCain, who has been no friend to Trump. The Democrats are going to hate to see McCain go.