What if when Luke goes to visit Ben, Ben lights his lightsaber first? That could go a long way to fixing what people perceived as a betrayal of Luke’s character. Will it completely win over most of them? Probably not, but I think it could still help.
How exactly would that work? Ben was asleep during the whole lightsaber-igniting affair. If you’re planning to have him wake up, ignite his lightsaber, and then show Luke’s “briefest moment of pure instinct”, that just sounds unnecessarily elaborate.
My personal favorite solution to the whole “Luke almost killed his nephew” thing is DonKamillo’s approach: Cut to black after Luke says “Snoke had already turned his heart”, and then cut to Ben looking at Luke (with the saber glow in his eyes removed). That way, it seems like Kylo saw Luke standing over him in his sleep and assumed the worst, allowing the whole Rashomon flashback thing to be kept in without Luke’s murderous instincts.
A middle way that I personally like best is SparkySywer’s version, which I’m using in my own edit. Luke looks at a sleeping Kylo and senses the darkness, ignites his lightsaber, and immediately deactivates it - then looks over at Kylo again to realise that he was awake the whole time, and heard it. Because he doesn’t stand there holding an ignited saber, it really does feel like the briefest moment of acting on pure instinct, and immediately coming to his senses.