The audience wouldn't be able to root for Han's killer anyway.
This is the big difference between Vader's redemption/Luke's vindication (the latter is more accurate, honestly) and the proposed "Kylo turns to the light" story idea - Vader never really did anything to the good guys outside of interrogation/torture. Outside of Ben (who basically doesn't
really die, and had a personal history we were unaware of to any real extent) Vader doesn't straight out MURDER a beloved character. He's the bad guy, but he never crossed that specific line. Han, Luke, & Leia all have their run-ins with him, but he's more or less just a really mean asshole. It makes it more palatable to believe that Luke could be right about him, because he hasn't really done anything on his own that's
too unforgivable on the surface
(although you could make the argument that he was a willing party to planetcide and probably murdered a whole TON of motherfuckers offscreen that we never heard of, yeah)
To contrast, Kylo Ren is going to KNOW that Han Solo is his father, and KNOW that he doesn't have to do what he's doing, and that he
can come back. It's kind of similar to the Ben & Vader fight, but the difference is that Ben has no intention of trying to bring Vader back. he's just gonna fight him, and hopefully kill him, and it only occurs to him to sacrifice himself when he sees the kids running toward the Falcon. But Han is going to put himself out there knowing, more than likely, he's dead at the end of this conversation. But he's gonna try anyway. And Kylo's gonna tell him to fuck off, and then murder him, and leave his dead body behind.
It's going to be a really, really,
really hard row to hoe to get the audience in a position where they're willing to accept that guy's "redemption," or to accept either Rey or Finn pursuing that option willingly.
And then the question is how satisfying could that redemption really be?