I would think a good writer would embrace such challenges and use them to allow the character to evolve further. This situation reminded me of how you originally described Jaime Lannister and his character arc after being captured.
Kirkman wants too much out of Rick. He's always the center of attention and the eventual leader of every group. Would it have hurt for Abraham to have taken the leadership role with Rick seething in the background? The existing conflict with Negan is indeed challenging to write because Rick should not be the leader to challenge the Saviors. Take aside Issue 100, and Negan becomes a far more interesting and compelling character to follow than Rick in the past 40+ issues since the hunters.
Maybe I didn't articulate it well enough.
What Kirkman was saying was more that by not having two hands, there are stories Rick can't explore and situations he can't put Rick in because it would stretch credibility beyond reader tolerance. He's essentially closed a shit ton of doors to himself as an author if he wants to continue to tell Rick stories. And I understand that.
As for Rick taking the lead in every situation, I think that by this point, it's fairly established that he IS a leader of men, someone other people in that world are willing to follow. Furthermore, it's natural that he would want to take complete control of any situation that his son is involved in. He wants the best for Carl, and in this world that means controlling the environment, as much as he can, that the boy is going to grow up in. Combine that desire with his natural skills and you have a situation where he's going to take control.
As for other characters taking the forefront and assuming control responsibilities, I feel that's been more or less organic. It would be far more contrived for other characters to suddenly become more prominent at the expense of Rick's role in things.
Some of the other characters are more interesting than Rick right now, especially the newer ones, but that's natural when Kirkman is making them stand out. Characters like Negan and Jesus. But I still am invested in Rick, and even though it's a guess I'd venture to say the success of the comic has a lot to do with the Rick-Carl dynamic.
I'm suspecting a major paradigm shift coming up, though. Not that Rick won't be around or that he won't be the leader (in fact, based on the most recent issue's events, it's fairly obvious that
More I suspect that you're going to see a whole cast of new characters somewhere else while Rick and co. rebuild. And eventually you'll see the groups meet up. That's just my guess, however.