Don't hold your breath on repair kits. It's a very difficult repair and you can't separate the butterfly keyboard from the top case. You have to replace the whole top case. The best you could maybe do is not replace the battery - but it's all glued. Good luck. I wouldn't attempt that sort of thing, and Apple doesn't.
I wouldn't be surprised if Apple bended that 4 year rule, though. But also realize that Apple will eventually stop repairing all computers just due to time passage. And also, eventually, from a financial perspective it's more cost effective to find a working used computer (after heavy depreciation) than to actually do a repair even if that repair is doable.
I do think that their replacement keyboards have better reliability than the early models. I didn't have any problems after getting mine replaced - I believe I used the replacement keyboard for around two years. But I still wasn't willing to keep the computer longer. I went straight from the 2016 to the 2019 16-inch MacBook Pro.
In any event, it was a nice opportunity for an upgrade. My 2016 was still worth $1000, and I ended up with 4 more cores, double the storage, and an absolutely massive increase in graphics performance. Using the education store and picking up in a state with no sales tax did a lot to make that price more palatable.