I think I've said this before, a while back. For all of Corbyn's weaknesses, I don't think its merely a case of finding someone younger/ stronger/ representative diversity-wise/ media savvy, who shares his politics and views. The problems in the Labour party, especially PLP just run deeper than that. A lot of Labour PLP is just diametrically opposed to a lot of re-nationalisation (utilities, even railways which is popular among voters), of the belief to build proper publicly owned housing, services. Let alone the really substantial challenges of globalisation, technological advance, etc. They say what some of their supporters want to hear, say the right things on social media when criticising Tories and cuts, but in reality, they're not offering any radical shift. They're great at the whole identity politics-based 'calling out' stuff and nods to social liberalism, but even the right has mastered that one in recent years, and its not the type of structural change that will significantly move the party to any proper left/socialist/pro-working class ground again. Corbyn's occasional drifting into any kind of once 'old left' territory is soon reigned in and 'clarified' by the Labour spin and PR machine. That won't change with a different leader in the same political vein.
I still think a split is the only way forward if any kind of proper left part of party is to rise from its ashes. I don't hold any hope though. I convinced myself for years to stick with them - 'well, at least it keeps the Tories out' in the hope of anything. I didn't particularly think Corbyn was going to really change much (I'd already left the party for dead some years ago now), but what I've seen despite his popularity with the CLP (although I do think the honeymoon period is over) is the way the most vocal and powerful part of the PLP machine has reacted to his leadership and vague attempts to swing 'leftward'. So, no, replace Corbyn with a newer/diverse model with the same politics - same problems will emerge imo.
