I’m going to say a similar thing to what I said about Electron and wlroots, which is that if we are going to proactively recommend this then I want to see proof that using a hardened memory allocator could have prevented a real-world exploit for somebody in the past.
Unlike with those two cases though, I think there might actually be evidence out there that using an alternative memory allocator could have some use in real-world scenarios, so I’m interested to see what stories/evidence you come up with.