Lack of previous experience in a community isn't necessary to provide leadership. As an ELT I could have gone from being the RLLCPO to being the RELCPO and succeeded. My base knowledge level of electrical systems wouldn't be why I would be sent there; my ability to manage the division, along with the DIVO, and the programs within the division successfully is what matters. To coordinate the division's interaction with the other divisions in Reactor Department as well as the rest of the ship. Taking care of all that "Navy" stuff that exists (to most nukes at least) completely outside of their job. For the subject matter expert part of it, I would rely on the First Classes and senior Second Classes. Those Chiefs didn't become SMEs after they put their anchors on, they got to that level of knowledge long before that.
I agree with most of what you said, but I think you are underestimating the amount of technical expertise it requires to be a successful division Chief. RL-Div doesn't really own much equipment that requires maintenance and repairs. Yeah, they have radiacs, sampling equipment, and a PSS pump that needs to be replaced every so often, but you don't tear those suckers apart if they break...you just turn them in and get a new one.
RC division is responsible for a lot of electrical gear which directly affects reactor safety. Additionally, it's possible that the 'senior 1st class' or 'senior 2nd class' is a guy who has been on board for 2 years.That is not a whole lot of experience, and certainly not enough to make up for a Chief who isn't the most technically savvy person in the division. A 2nd tour 1st class? He might be the most experienced, but there's a reason he didn't make Chief so he's not the guy you'll want to lean on. This ties into why I think it's a bad idea to reward nukes with increased rate instead of increased bonus pay. During complex evolutions like rod testing or calorimetrics, the RCLCPO is expected to be able to take the lead. When you get an unexpected LED on one of the cabinets, the RCLCPO is expected to take the lead in troubleshooting the problem.
What you detail is how larger forward divisions like Sonar worked...1-2 second tour 1st class petty officers who are technical experts, mentored by a Chief who provides leadership and fills in the gaps if the 1st classes can't get it.
Additionally, the fleet has also moved toward pushing Chiefs into taking a more hands-on approach to maintenance, particularly with RC Div who, in NR's view, keeps screwing up. That means requiring him to be there to supervise all RC-Div maintenance that could affect reactor safety, which is practically everything, to ensure that it's done correctly and standards are enforced. Even outside RC div, there was a push from squadron that 'the Chief is the work center supervisor.'
On my ustafish the eng dept Chiefs were the really technically savvy Chiefs, while the forward Chiefs were better at handling discipline and enforcing standards. When an eng dept Chief didn't know the answer, he at least knew how to research the problem and find an answer. Forward Chiefs didn't even know where the tech manuals were half the time. Thus we had the EDMC troubleshooting navigation equipment at one point. Unfortunately, very few were a combination of both.